Susan Hill barrels around the corner to our table, which is tucked away in a noisy alcove of the bar at the Covent Garden hotel in London. She looks pleased to see me, if a little apprehensive. That is not surprising: this week, she set off a storm of outrage that had her running for cover as much from her publishers, Chatto & Windus, as from the keyboard critics who piled in on social media.

In an article in the Spectator, she announced that she had pulled out of an event because the bookshop concerned was promoting anti-Trump authors. It was not: the Book Hive in Norwich, which outed itself as the target for Hill’s ire, was merely the conduit for novels about totalitarianism donated by a local reading group as gifts for customers. The books included George Orwell’s Nineteen Eighty-Four and Margaret Atwood’s The Handmaid’s Tale.

Hill sits down with a thump. She is a small woman who wears her peppered hair cut short. “How are you?” I ask. Although in emails the day before she was adamant that the Book Hive debacle is off the agenda, she seems relieved by the question. “One small article and the world went mad,” she says, clutching at a necklace of oversized turquoise beads. “Have they got nothing else to worry about?”

It sounds disingenuous. I look the 75-year-old writer of The Woman in Black in the eye; she returns my gaze steadily. “No,” she says, to my unasked question: surely someone who has written more than 30 books, from ghost stories to crime novels, short-story collections and literary novels, cannot be naive to the impact of an article in a national magazine denouncing an independent bookseller? She drums her fingers on the metal table. “I don’t want to talk about that, because this is not about that and the publishers will kill me,” she snaps back. In an instant she adds: “Frankly, the less oxygen you give it …” Her initial bluster disappears with a sigh, like air from a balloon. “It’s all about nothing. Has nothing happened in the world that people go crazy?”

The spat has shaken her, however, and although she has told me she will not talk about it, she alludes to it throughout the interview with shoulder shrugs, sighs and comments. Before we part, she says of the Book Hive proprietor, Henry Layte: “If he rang up and said, will you come and talk to us, of course I would. Only if he said he wanted me to. I wouldn’t want to walk in there uninvited.” She adds hastily: “I don’t suppose he would let me in his shop.”

But she has not invited me to London to talk about that, she insists. She wants to talk about her new novel, From the Heart. A slight tale of 211 pages, it is a coming-of-age story set in the early 1960s. Olive Piper is an awkward and bookish teenager whose escape from home is blighted by an unplanned pregnancy and then a doomed love affair with another woman. It is written in the Whitbread winner’s characteristically pared-down style – not a word wasted – which adds great impact to the book’s two big reveals.

And there is one particular aspect of the novel Hill particularly wishes to talk about: Piper’s love affair with another woman, because it has parallels with her own life. “The unexpected happened to me: I fell in love with another woman who fell in love with me.” The woman is screenwriter and producer Barbara Machin, creator of Waking the Dead, for whom Hill left her husband of almost 40 years, the respected Shakespeare scholar Stanley Wells, six years ago.

Taking a sip of ginger beer “with lots of ice”, she begins to say more, but her words are drowned out by the clatter of empty champagne bottles being upended into an ice bucket at the bar, followed by the loud rasp of the cappuccino machine. She throws a sharp look at the barman and we wait in silence until the noise subsides. The love affair with Machin bloomed over drinks in Cotswold pubs, where the two would meet to discuss the screenwriter’s adaptation of Hill’s Serrailler series for ITV. “We had met in Cheltenham because I was doing some gigs at the festival,” Hill recalls. Although she regarded her future lover as “a very nice woman” when they met, she says she was “just shellshocked” at the gradual dawning of a love affair.

She says it was her first adventure into same-sex relationships – apart from a crush shared with other girls on a geography teacher at her Scarborough convent school. “She got married and we were all devastated.” For a moment her voice, from which Yorkshire has long since been scooped out, becomes wistful. “It absolutely never crossed my mind that I had any attraction for women or was attracted to women,” she adds. Three years before marrying Stanley, her heart was broken when her fiance, David Lepine, the organist at Coventry Cathedral, died suddenly of a heart attack in 1972. “He was the love of my life,” she says, and insists that throughout her “long and happy marriage” she never had an inkling that she might not be straight.

“You fall in love with the person,” she says, with another twist of the beads. “That person could be the same sex or the opposite sex, but you fall for that person. And I felt very much that [Barbara] was somebody whom I liked.” Machin was “very warm and attractive”, she continues, then laughs. “The woman thing, I thought, ‘Heavens!’” Her eyes pop at the idea.

Photograph: Linda Nylind/The Guardian

As she speaks, I become aware how Hill has softened her appearance since I last saw her, 10 years ago. Back then she dressed like a Gloucestershire landowner’s wife, in brogues and Barbour. Today she wears coordinated bright colours: a long-sleeved cotton top matches the beads, and a bright red handbag on the floor beside her matches a red undershirt only visible at the neck. The ensemble suggests a confidence about her appearance that I haven’t seen before.

In a trade in which the cliche is to be a Hampstead liberal, Hill stands out for her forthright support of the Conservative party, of which she is a member. And while other writers will not be surprised to hear that she is a party member, they will be surprised by her claim that, “I’m not very rightwing. I certainly wouldn’t be Ukip or anything.” That may be true, but some of her closest and most vocal supporters number among the most vociferous elements of the libertarian right. Asked where she places herself in the political firmament, she replies: “Theresa May. Trouble is, I don’t know any of them any more.” She does know Michael Gove, however, who stepped into the row over the Book Hive with a tweet that said: “Susan Hill is a brilliant writer and her detractors are illiberal bigots.”

Essex Serpent writer and Norfolk-based novelist Sarah Perry bit back at Gove with a tweet saying: “1. Nobody queries for a second her genius, MICHAEL. 2. Disagreeing is not ‘detracting’, MICHAEL. 3. It is not bigoted to disagree, MICHAEL”. This was on top of comments directed at Hill by the likes of the Father Ted creator, Graham Linehan, who tweeted: “Ha! Even fonder of my local bookshop now. What a stupid crank Susan Hill is.” Hill will not answer questions about Gove’s involvement, but their friendship is strong – Hill has defended the would-be Tory leader on threads posted about him on Facebook. What she will say is that her support for May and Gove is firmly tied to their stance on Brexit.

Again, it is an unusual stance to take among novelists, who last year were overwhelmingly in favour of remain. Why does she want to leave the EU? Her response becomes less coherent than anything else she has said in our interview: “I voted to leave because ... I am old enough to remember very clearly the last referendum ... I am not sure about this ... but watching over the years more and more rules coming to us from an unelected body ... I don’t mean just the stupid things to do with health and safety, but taking away every country’s individual national decisions ...” Her words fade out. When I challenge her about the truth of this, she shrugs and replies: “Anyway, I just think Brussels costs so much money.” Like her criticism of the Book Hive, it seems as much about supposition as information.

Hill is also a devout Christian, a high Anglican, but doesn’t see any contradiction with coming out as gay. “I long ago gave over any anxieties about that,” she says with a wave of ringless fingers. The break up of the marriage has been “very amicable”, she insists. “There have been no harsh words.” Wells, she says, is happy to be “queen bee” in Stratford-upon-Avon, and there are no plans to divorce. The marriage, she believes, would have ended anyway. “You do pull apart. Once your children leave home, you either become a tighter unit or you become the opposite, and that happened to us.” Her daughters, Jessica and Clemency, although shocked at first, have settled into a good relationship with Barb, as Hill refers to her new partner.

But the parallels between the writer and Olive are not just about sexuality. Born in 1942, Hill would have been Olive’s contemporary. Both were awkward teenagers, whose bookish demeanour masked a shoot-from-the-lip habit that speaks first and asks questions later. Hill blames her inability to watch her words upon her Yorkshire childhood. “In Yorkshire they will say what they think and people will say, ‘How rude!’ But it isn’t meant to be. It is meant to be just straightforward.”

Straightforward it may be, but forthright criticism of friends on Facebook has left wounds. “She somehow feels she has the right to take people down a peg,” one such victim confided. “She can be cantankerous,” says another, “yet she inspires powerful loyalty.”

I'm not very rightwing. I certainly wouldn't be Ukip or anything

She looks genuinely shocked when I say this to her. Kindness is important to her and the idea that she has left friends smarting after voicing her opinions on social media stings. “I don’t think I write many unkind things ... I try really hard ...” she says, all bluster gone. That she is kind is attested by many women who have received her support – given quietly and without fuss – when their relationships have turned abusive and they have needed to escape.

Hill herself has been calloused by painful experiences in her life. As well as the death of Lepine, she had several miscarriages after the birth of her first daughter, the novelist Jess Rushton, and lost her second child, Imogen, five weeks after she was born. A hand-painted box given to her at the time by the writer Bel Mooney remains a treasured possession. “However you lose a child,” she says, “all sorts of people come out of the woodwork and, even if the circumstances are different, tell you that it happened to them. It is a real human bond.

Like Olive in her novel, Hill was told by her mother from an early age that she was not attractive. It still pains her. “When your mother says: ‘Oh, no one will ever look at you, a plain face like that,’ you believe it, don’t you?” she says, the confidence punched from her face by the recollection. In the book, Olive’s schoolfriend Margaret Reid is “the pretty girl who was seen in town with her boyfriend”, Hill says, admitting that such girls were granted a confidence about life that she never had.

The photographer interrupts us. It’s time to take her picture, and her partner is waiting for her. I have one last question: why did you defend Trump? She splutters in disbelief. “I am not pro-Trump!” she almost shouts in reply. “People should read what I wrote,” she adds, then: “But I am not talking about that.” But she looks at me again and says: “Really? Do people think that of me?” I point out that she has been off Twitter for a few days. “Christ!” she replies. “I’m a Conservative. I am not a Trumpian Republican ... apart from anything I think he is not very bright.” With that she scoops up her things, gives me a hug and scurries out of the bar in pursuit of the photographer.

• Susan Hill’s From the Heart is published by Chatto & Windus. To order a copy for £9.34 (RRP £10.99) go to bookshop.theguardian.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99.