I have a friend who is obsessed with her figure. She keeps telling me how fat she is and in fact she's just a normal weight. But she goes on and on about it, and it's driving me mad. She's always trying diets and no matter how much I tell her she looks great and she doesn't need to do anything about her weight, she can't stop. I'm starting to feel it is something of an obsession. We can't talk about anything until she's gone through beating herself about how she looks for about half an hour. How can I help her? Yours sincerely, Zara

Virginia says... The way to help her – and you, by the sound of it – is to break this pattern. And since she's clearly not going to stop, then you're the only one who has any power. Why does she obsess like this, demanding your reassurance? Is because she's genuinely worried about her weight or because she craves attention? I mean, if you succeeded in reassuring her about her weight, would she then start on something else – her nose or her personality? What do you think?

If it's her weight she's really worried about you can try a variety of tacks. The first is to ask if she doesn't think she's becoming a bit obsessed about this. Stop her in mid-stream and put your cards on the table. "Look," you can say, "every time we meet you go on about your weight and every time, I reassure you. Have you thought you might have some problem with this obsession? It's clearly blighting your life. And you're clearly not fat. As your friend, I'm worried, not about your weight but your obsession. Why don't you try cognitive behavioural therapy?"

Another method would be to stop reassuring her. The problem with reassuring people too much is that by reassuring, you're colluding in their anxiety. By saying "Oh, you're not too fat" what you're really doing is agreeing with her that being slightly overweight is a terrible thing. Why not say "Well, yes, I suppose you are a bit plump, but it suits you – I'd stay the way you are." That would stop her in her tracks. That's why if someone thinks they've done something awful, rather than saying that it was understandable or that they won't be found out, or that the person they did it to deserved it, it's better to say: "Yes, it was an incredibly mean and horrible thing to do. We all do horrible and means things sometimes and this time it's you who've done it. You're going to feel terrible about this for ages, I'm afraid. There's nothing that can be done about it." Then at least you're acknowledging the fault, but still accepting the other person as a friend.

Another way out might be to leap in first with some anxiety that you have, for a change. I'm sure you can find a worry – most of us have tons of them lying around and even if they're not lying around, we can usually find a few in a back drawer. Before your friend has time to get on to her weight, get the conversation going around your problems for a change. You could try one of these or each of them one at a time.

Readers say...

Change the subject

Your kindly reassurance is what feeds your friend's obsession, so she engineers the conversation accordingly. Try new tactics. You could agree with her: "Yes, you keep saying so." Assuming you see her fairly often, there's no need to ask her how she is, simply ask: "What's new?", and if she starts on one of her me-me-me rants, repeat the question. This is the old assertiveness technique called "broken record", to divert someone and not fall in with their, possibly subconscious, schemes. It helps to have another topic in mind, ready to switch into as her jaw drops at your audacity...

Sally, by email

She needs tough love

All groups have their own, well-understood, method of greeting each other. Old people say "You look well!", the Queen asks if you have travelled far and women talk about their weight. It's preparation for the real conversation. Your friend's mistake is to spend too long in this greeting period. But why should she want to leave this happy place, if you spend it stroking her ego and telling her she isn't fat? You need to show tough love by refusing to play along. Tell her once and once she isn't fat, then firmly move the conversation on.

Felicie Oakes, by email

Next week's dilemma

Dear Virginia, I'm just about to go off on a gap year before I start my studies at university, but I'm really worried. My Mum and Dad have always smoked dope in the evenings occasionally, even though I've never liked it much. But Mum told me last week that Dad is hooked on cocaine and she's worried sick. He's spending too much money and he's getting paranoid, even though he still works at the advertising agency he's always worked at. I feel I can't leave Mum alone, but so want to get away. Should I go away? What can I do? Yours sincerely, Georgie

What would you advise Georgie to do? Email your dilemmas and comments to dilemmas@independent.co.uk, or go to independent.co.uk/dilemmas. Anyone whose advice is quoted will receive a £25 voucher from the wine website Fine Wine Sellers (finewine.sellers.co.uk)

Virginia will appear in her one-woman show, Growing Old Disgracefully, at the Gilded Balloon at the Edinburgh Festival