My Best Friend stole from me?

At the end of last summer I had a purple lace bra that went missing when I was packing my clothing to go back to school. Right before I noticed it missing I saw the same bra in my best friend's purse when we were hanging out. I told her I have that same bra and she told me she had just bought it at American Eagle which I thought was weird because I found it at Marshall's so I don't know why it would still be in the store but I let it go, even though I now suspect that she stole it from me. A week ago she slept over after a night out and I left her alone in my room for an hour in the morning when I went to help my grandma with something. I came back and she told me how she tried my shatter OPI nail polish but it didn't work. Today I went in my nail polish to paint my nails for the first time since before then and I felt like I didn't have as much as I thought. I went through my nail polish looking for the one I was planning on using and found it missing. I also noticed at least two others, both purple, were missing. Her favorite color is purple and she was the last person I know of to be in my nail polish. I really want my nail polishes back if she took them, especially because one is a limited edition I spent 3 weeks looking for and the other is one of my favorites. How do I confront her? She's my BEST friend and I don't even know if she actually did take them...