AITAH for locking up my food so my roommate would stop stealing it?

I (26F) and I live with two roommates, K (26F) and L (28F). For the most part we get along, but K has a habit of eating my snacks. At first it was small things like finishing my bag of crisps or taking a scoop of my ice cream. I ignored it the first few times because I thought it was a one off.

It kept happening though. Almost every week I would go to grab something and it would either be half gone or missing completely. I asked K several times to stop and she would say sorry, but then a few days later she would do it again. At some point it started to feel like she just assumed my food was there for everyone.

After months of this I finally bought a little lockbox that fits in the fridge and freezer so I could keep my stuff safe. When K saw it she got upset and told me I was treating her like a child and that I was creating distrust in the household.

I told her that I only bought it because she had ignored me every time I asked her not to take my food. Since then she has been sulking. L told me I should have just let it go because this is what happens when you live with people.

From my perspective I do not think it is unreasonable to expect food I bought with my own money to stay mine. But now both of them are annoyed and I am second guessing myself.

Am I in the wrong for locking up my food?