Betty Dodson is back. The pensioner once dubbed the "godmother of masturbation" thanks to her 1973 bestseller, Sex for One, is relaunching her masturbation masterclasses in New York. Now 85, Dodson wants to help the post-Sex and the City, post-Girls generation of women that she believes are not nearly as liberated as they think they are. "Most of them haven't even seen their genitals in a mirror. You show 'em and they go 'eek!' Or 'ugh!'"

Her comeback has caused excitement among a new generation of American women, many of whom are seeking inspiration from the feminist thinkers of the 1970s in the face of renewed attacks on women's rights. "Yeah, I'm an overnight success at 85," says Dodson as she breaks into a chuckle and pours me a glass of vodka. "People now say THE Betty Dodson."

We meet in her rent-controlled apartment on Madison Avenue where she has lived since 1962. Dodson arrived in New York, fresh from Kansas, in 1950 to train as an artist; the walls of her living room are lined with her own paintings of erotic couplings and blown-glass sex toys. When she held orgies here in the 1960s ("there's no furniture you can't move") she realised that many women were faking pleasure. Her original women-only masturbation – "bodysex" – classes took place here from the early 70s for 15 years with an ideal number of 13 per class.

Although she was described as one of the "early feminists" by Gloria Steinem, she felt out of place in the consciousness-raising groups of the time. "I always thought sex was a top-priority issue," she says, pouring herself a whisky. "Feminists like Gloria Steinem thought it was private." (She chuckles, "I love Gloria. I used to call her 'the general'.")

Dodson has a mouth like a sailor and the easy manner of a wisecracking Scorsese character. She looks incredible, with a zest for life that belies her age. She credits "masturbation, pot and raw garlic".

Betty Dodson in the 60s. Photograph: Handout

When you read Dodson's 2010 memoir, My Romantic Love Wars, she doesn't strike you as a swinging-from-the-chandeliers type. In 1959, she married Frederick Stern, an advertising director and pushed herself into sexual self-discovery when the marriage ended in divorce in 1965.

She says she was 37 before she met her sexual match, Grant Taylor, a 42-year-old English professor from New York University. Taylor convinced her that her inner labia lips weren't deformed and introduced her to the idea of "electronic orgasms" (thanks to his electric scalp massager), as well as the idea of non-possessive love. "I'm a romantic love junkie just like the rest of you," she shrugs. "It's a disease, I don't know how else to describe it." She says that feminists are often the worst culprits. "They're afraid of sex because they say it's too controversial. But I feel it's because they're personally too conflicted. They don't want to masturbate, they want Prince Charming. It's Walt Disney. Puke. Barfarama."

At her first group sex party on the Upper East Side, she admits she was "a typical Virgo at an orgy," as she nervously removed her new black lace knickers and folded them under a chair.

But now, after 50 years at the frontline of the sexual revolution, Dodson's work is being rediscovered by a new audience. Some are young, fashionable types who seem to have it all but – she says – have never had an orgasm.

They're usually too shy to attend the bodysex groups and opt for private sessions; she had a 25-year-old in yesterday for a lesson in self-love. "Poor girl had no idea. Never masturbated as a child." Dodson says her biggest fans are fourth-wave feminists bored with the right-on, anti-pleasure stance they feel third-wavers stand for; for them, Dodson's message of rediscovering your power through getting into your body and independent orgasm seems much more attractive than banging on about childcare and sexual violence.

"In the workshop we share our orgasm with the group while being in control of our own clitoris," she says, explaining that the class consists of a "genital show-and-tell" followed by masturbation in a circle. Betty has been known to help out with her vibrator.

"No wonder I keep doing it. Are you kidding? The sounds, the sights, the smells. Fat, skinny, one tit gone. Women are so beautiful."

In 2006, Carlin Ross, a former corporate lawyer came to interview Betty (who defines herself as a "heterosexual, bisexual, lesbian") for her website. Ross, now 41, says Dodson was "one of the few sex-positive feminists and that had always intrigued me". She recalls how, halfway through the interview, Dodson reached across the table and announced: "We're going into business together. Shake on it!"

Ross gave up the day job and has now become (purely platonic) business partner and heir apparent to Dodson's empire. She is archiving Dodson's work online and can be credited with persuading Dodson to revive her workshops. They began slowly last year, and cost $1,200 (£720) for a weekend. A teaching programme for women who want to spread the Dodson word was introduced this year. "Women tell me they worry their fantasies aren't feminist enough. I tell them: 'Honey, the dirtier and nastier, the better.' I have a Rolodex, a whole series. My fantasies are so dirty, they'd put me away."

The trouble, she says, is that women are "so addicted to romantic love. It's the heaviest drug in the world and we make long-lasting bad decisions because of it."

She doesn't believe in monogamy. "You get married, you give up sex. Pretty much count on it."

She says the "best sex of my lifetime" was in her 70s when she was "training" a twentysomething called Eric. After 10 years she decided to let him go. "You have to let the young ones go. You don't want to be Hugh Hefner."

Her message – keep up a sexual relationship with yourself, you can have first-rate orgasms by yourself; stop doing what you think your partner wants to see in bed – seems more necessary than ever in an age when increasing pornification of our culture is making these ideals harder for women.

As I leave, she gives me a hug goodbye and tells me to "spread the word!".

• Betty Dodson's Bodysex workshops