Dear Mary: How can I stop my sister-in-law pinching food off my plate?

Q. Since the relaxation of lockdown, my brother and his wife have started coming to our garden for takeaway meals. My sister-in-law always says she isn’t going to eat at all, so we mustn’t order anything for her. But when the food arrives, she gets a fork and enthusiastically begins picking off everyone else’s plate. Sometimes she just uses her fingers. I do like her very much but, as they married just before Covid, I feel I don’t know her well enough yet to comment or to suggest she orders something for herself. I am always left feeling slightly hungry and a bit irritable, as the whole time I am anxiously anticipating what she will help herself to next. My brother clearly doesn’t mind and my husband, who has perfect manners, pretends he doesn’t. Any suggestions?
— Name and address withheld

A. Why not announce you have embarked on a ratio-controlled diet: for example 30 per cent carbs, 30 per cent vegetables, 40 per cent protein? When the food arrives you can briefly, but theatrically, weigh and calculate your own ‘portion’, claiming you are preventing yourself from having too much or too little.