Try approaching (don’t know if you already have as I haven’t read the other posts). And in a non-accusatory talk to her and make up a story/example if you have to. “You know, I think it’s odd that some of my food is missing. In my old dorm, people assumed that they didn’t have to ask to eat your food. It’s nothing short of stealing. And now my food is disappearing again. Maybe I’m losing track of my food or there’s a jinn in this apartment.”
If she gets defensive and says, “Are you accusing me of stealing?” Just say, “No, I’m not accusing you. Just surprised that my food is disappearing again.” Maybe, she’ll feel enough of a guilt trip to be more careful. Not a guarantee, but sometimes sneaky hints can work.