Let her steal it if she can bear it. Anyway, this kind of person will pay for it one day. What he does in secret can't be hidden, and it will be made public one day. In fact, it is easy to solve the problem if you can't stand it. You can pretend not to know what she stole. When your other roommates are around, you can pretend that you can't find them. If she takes it out for you, forget it. After all, she is a roommate. Pretend to know nothing and say nothing. You can wait until you accidentally see it at her place and say how your things were found here that day. Don't use too much reproachful tone. After all, being a roommate should not be too ugly. Of course, you should also make sure that this is your business. Generally speaking, she can't deny it, otherwise once you misunderstand her, you will be embarrassed and others will not understand.