Is it illegal for a co-worker to get into your purse while you are on a break, make copies of documents and/or a flash drive?

My supervisor informed me she read a document of mine that could only be found in one of 3 places: on a printed document in my purse, on a flash drive in my purse, or in my home. My co-worker works beside me and could have obtained it while I was on a break, possibly even making a copy of the documents or my flash-drive. If I asked, my supervisor would probably not tell me how this happened. However, my co-worker advised me to look for my mothers birth year on her license - which is found in my mothers purse! They were most likely looking for notes on a possible workplace bullying harassment suit, which I will not be filing. Earlier the :"bully" announced to me she was documenting on me. Then I had to document too. They saw me writing notes (memory problem)- I am also on camera.