What should i do about my room mate?

ok so heres the deal my room mate gets on my nerves pretty much all the time.. shes a foreign exchange student thats only going to be here for fall quarter.. so over all we get along but she does these little things that annoy me.. for example… when im away for the weekend she goes crazy, she touches all my things she unplugs my air freshener (which smells WAY better than her.. aparently she hasnt discovered deodorant) .. anyways last week i had some food in my fridge (which i let her use) and when i got back it was gone.. she freakin ate my food.. and when i saw her she said that she was hungry so she ate it.. (she has 19 meals a week..i have 10) .. she left my fridge open after eating my food.. and when i got back it was a disaster .. and there was water everywhere… during the week i like to go to sleep at like 1030 and shes likes to go to sleep at 3AM!!. today i had a class at 8am.. and i got up at 745.. cause i was soo tired and couldnt go to sleep until 3am.. shes up all night on aim and she types so loud.. LIKE OMG!!

I DONT KNOW WHAT TO DO… i dont wanna be a big b**** cause shes only here for like 2 more months.. but i cant stand it anymore… i was thinking about locking my fridge and see how shes reacts to it.. (my fridge comes with a lock..lol)

i dont know what to do.. anyone have advice.?

AND i believe that i ama good room mate.. i dont even bug her.. i have only had one friend over once.. and it was like for an hr.. and she brings all her friends over.. at like 1 am