Roommate dumps food on my belongings

I live in graduate student housing at a university. I was paired randomly with three roommates. One of which has been stealing our food and the rest of us have all addressed it with her. We’ve let her know that we’re happy to share but please ask. It however keeps happening and I said if this continues I would report to housing. I never did and it was fine for a few weeks.

Just a few days ago I start seeing my make up and skincare in our common sink area just on the floor and ramen in my sink. Today I found it over my shoes. I’ve checked with my roommates and the other two have said it’s not them and they weren’t home during the time it happened either. The one in question hasn’t said anything.

I reached out to housing but honestly don’t what I can do. Would appreciate any advice.