The actor, 59, on escaping small-town America, her alcoholic mother, and why she still thinks about the last line of Four Weddings

I asked someone the other day what people think of me and they said: “Unattainable, but relatable,” which is an oxymoron. The pictures of me out in public are me all dolled up. What people don’t see is I’m kind of goofy. My kids can attest to that. And while I try not to take myself too seriously, I really think things over. I analyse my history and I bring it forward to make my present better.

Watching the unfolding of my mother’s demise was hard. She was an alcoholic. She’d been a schoolteacher, but kept losing her job. We ended up working at McDonald’s together when I was 16. One day I was driving her in and thinking: “She’s not quite sober, but I think she’s sober enough,” and she got fired. I asked them to give the job back, but they wouldn’t, so I quit. It was her last job. When I was 17 I did an intervention with her, but it failed.

Four Weddings and a Funeral was a luxury. The settings were so romantic, the writing was perfect and Hugh [Grant] was such a talent to be working next to. In Groundhog Day, Harold Ramis [the director] loved me as an actor, which makes it really nice to go to work every day.

Nobody explained to me what I had to do. When I was 20, I left South Carolina for New York with $2,000. I didn’t know anybody outside my environment. On one of my first big jobs as a model I remember going to dinner and everyone was talking about plays and books and all this stuff I hadn’t been exposed to. I thought to myself: “I need to go to plays. I need to read more books.” It was brand new and I thrived.

Caring for my father was a beautiful resolution to a not-always-perfect relationship

Have open conversations with your children about personal relationships. I talked to mine about what’s healthy and that it’s OK to enjoy kissing. When I was 14, I got diagnosed with mono [glandular fever]. My father drove me home from the doctor’s without speaking and made me feel dirty and like I’d done something terrible for kissing somebody. It taught me to never make my children feel bad about themselves for something like that.

I think it was my sense of humor and realness that people liked. I’d turn up to fashion shows in a T-shirt and jeans. When I went for the interview for the Calvin Klein commercials they said: “We hear you’re funny,” so I showed them some made-up stories I used to do with my friends from home about two characters called Dot and Earl. They ended up using it in the commercials.

I’ve thought a lot about the line: “Is it raining? I hadn’t noticed.” [MacDowell’s line to Grant at the end of Four Weddings.] I don’t think there’s anything wrong with it and I don’t know why people pick on it, but I’ve thought about what else I could have done. Should I have looked around and said it as a joke? I don’t think so.

Caring for my father was a beautiful resolution to a not-always-perfect relationship. The last year of his life he had dementia and I got to spend a lot of time with him. That was cathartic for me. I don’t think he was great at a lot of stuff, but I still loved him and forgave him.

I wanted to give my children a normal life. They rarely went to openings or premieres. We’ve never spent much time watching my movies. When I came home I never talked about my work, I just talked about them, and I was their mom.

Only The Brave is available on digital download from 5 March, and on Blu-Ray, DVD and VOD from 12 March