What can I do about a thief in the family?

Someone close to me has on several occasions stolen from me, I have no means of securing all of my possessions from her.prying, thieving fingers. She has invented stories that I have stolen and sold her own possessions and uses that as a means to justifying her own actions to randomly take treasured photographs, jewelry, computer parts, and clothing items from me and hold them for ransom against the things she thinks I've stolen. Occasionally she gives these treasured items away to charity because she really believes I've taken her treasured worthless trash and sold it on EBAY only to have them turn up months later in her own room under a pile of shoes. I've never stolen from her, not once. At this point I've moved my jewelry collection to a trusted friend's house. I fear to leave the home to go work because she might take another photograph or some other treasured object. I'm not allowed to keep photos on my desk at work, and hauling around dozens of photos in my purse is impractical. Last week she took $20 in coins out of a coin collection I'd been accumulating for the past 14 years. Today she paid me $20 back in a cash bill and admitted to the theft, which I had been unaware of until tonight. I really think she's gone too far, and I need to find a way to stop her soon. I would like to know the right words to say to her to get her to stop.