My New Roommate is a Thief, What should I do?

It hasnt been two weeks yet when a new roommate joined our dorm. I introduced myself to her but she wasnt really up to for a conversation so i shrugged it off thinking shes the quiet type. Turns out to be the SNEAKY type. The day before esterday, my wallet went missing, it was morning and the First day of exams too so I had little time finding it. I quickly messaged my sis (also my roommate) asking if she brought it w her but she said no. My sister told me where she last put it. Clearly wasnt in the spot she mentioned when I looked for it. It was rlly suspicious cuz it normally takes less than a minute finding my wallet whenever I misplace it. So I went to my exam room pissed and anxious about the missing belonging that it made me finish the first subject in mere 20 minutes (70 items). I sprang back to dorm (literally 1 mins away from university) before I take my next exam, told my other roomie (whos already been at the dorm for a few months long) through chat. When I looked at the place my sister put it, the wallet was there. Well, it wasnt there earlier, Im sure of. When I counted the money in there, few coins were missing (i recall that she has a coin bank (piggy bank) and she puts spare coins for her savings). I was mad w the fact she went sneaky w my PERSONAL belonging (i wouldnt mind if it were a dish soap i bought). she was fake sleeping and had her face stiffly covered w a blanket. It was really awkward for her ig when I told my other roomie outloud that I had a police uncle along w mentioning exagerrated stories to scare her off from doing it again. Give me tips on how to respond to her action better if she ever did somethin similar again.


lil observation after the coin fiasco: And last night, she returned drunk and reeks of cigarette. She doesnt go to my university (my dorm isnt a univ dormitory)