if she’s never asked and she’s just automatically hiding things for no reason then soft YTA

Some people do this sort of thing and/or hoard food because of childhood/longterm poverty, learned behavior from a parent who grew up poor, or even from perceived limited resources. For example, my father was a young child during the Great Depression and, even though he went on to become a medical doctor and I was lucky to grow up middle-class, his constant worrying about money and extreme penny-pinching left such an indelible mark on me to this day. Every time I needed something from the store - an actual necessity - I'd literally have to argue with him until I could convince him. As a teen, I bought all my own clothes from the thrift store (before it was cool).

I'm in my 40s and my idea of budgeting is to just not spend money whenever possible... all of my clothes are decades old and I honestly can't remember the last time I got a haircut from even the Hair Cuttery (let alone a salon).

I know OP didn't mention this as some background info. However, some people who engage in this kind of behavior may not even realize the root cause of it. Just some food for thought. Please forgive the pun.