I have what I believe to be quite a serious problem. My brother-in-laws girlfriend is a liar and a thief. She has physically attacked me twice while my children (3 and 2) were present. She has accused me of stealing her make up and clothing (I very rarely use make up and would never use make up that somebody else has used and she is also 2 dress sizes larger than me) she has accused me of lying about my two miscarriages one that I had before she and my BIL knew each other and one that I had in July last year. Each time she has attack me, she has guilt tripped my PIL into allowing her to live in their house (she moved herself in when she got together with my BIL, as her mother couldn't handle her anymore) as she had no where to go (she has family in the area that offered her a place to stay) and the second time she had a miscarriage 4 day before the incident (she on the implant, so unless she had it taken out and not told anyone or it has fail, which is highly unlikely, surely there isn't much of a chance this is true). She has also accused me of send vile messages to her via Facebook (I didn't have any access to face book when two of the messages were sent as I was in a meeting and I highly suspect that she sent the messages by setting up a false Facebook account in my name).
Today I spotted my set of cosmetics, that I have been looking for since Christmas as they were a gift from my partner, under her bed, a load of my missing makeup and my late grandads razor and bag.
Do I expose her for what she really is? Do I tell my mother in law what I have found out? Do I keep quiet about the whole thing and move on?