Thanks for all your replies!
I've lived in a quite a few share houses before, and to be honest I also prefer living with guys but there aren't always that many options. This house is pretty much perfect, low rent, huge backyard for the dog, and the flatmates are actually really nice and I get along well with them, great cleaning roster, no lease (great for me) etc. Except for this food issue.
I just don't want to do shared food. I don't mind that people take my food sometimes - acceptable losses - but I want to go out and buy my own food whenever I want. If I want to spend a ridiculous amount on organic, local produce that's my choice to make. I like going to markets on weekends and buying what's in season etc, but spending all my food money on the house kitty means I can't.
I just don't know how to approach this. We do share things, and we each cook one night a week and the main flatmate is really into this (the other doesn't care too much) and when I tried to change/talk about it last night she was not even remotely flexible and I am concerned that if I push this enough they'll ask me to leave.
I just want some ideas of ways to approach this person (can you tell I'm not a people person
) or things I can do to make her chill out etc.
All I can think are passive aggressive type things, like spending a lot on the weekly shopping that blows the budget or something, so it stops being viable, but I don't really want to do that. I just want to buy and eat my own food. And I don't know why that's a problem, every other house I have ever lived in has done it that way.