My sister has been stealing from my house for years, what should i do?

My sister is 10 years older than me, for at least 4-1/2 years she has been getting in to my house and stealing money, among other things from me. I do not have a lot, but what I have is mine & I have worked very hard for it. When cash began disappearing from "hiding places" in my house, I first began to blame my teenage boys for it. Subsequently, on 1 occasion, my ex-husband busted her at my house without my expecting...he had brought our boys by to get something & she was coming out. When they asked her what she was doing, she said she was borrowing something (or a similar excuse). They asked where her car was, as she had parked a block away (telling me she was up to stealing, again), again she had some "story". At the time, being my only relative in town, she had a key to my house. After that I changed the locks & the problem ceased as long as everyone remembered to lock the door. I had even caught her red-handed a couple of times. In the past year, there has been an incident with her sister-in-law. They had a big "falling out" details about which I was not privy, until today. I called her sister-in-law and found out the reason she had "banished" my sister from her & her mother's home was because, for about 5 years, there had been some question about missing $ in various settings: her daughter's shower, wedding, and her mother's home. She could not believe my sister would do such a thing; they had always been so close. But so many instances had occurred, that she hooked up a surveillance camera in her mother's room & caught my sister on tape. She confronted her brother (my sis's husband) & got nowhere. I similarly spoke to him and their children, to no avail. Last Wednesday it happened again. I had stashed $75 cash in a crystal bowl...& my son said it was a bad idea knowing my kitchen door lock was broken, I should've listened to him...after working a 10-1/2 hour day, I came home to find $35 where I had left the cash the night before. A random thief would take ALL the cash, not to mention various other valuables. I know the old saying, "the only thing locks do is keep your friends honest." But this is ridiculous. She has diagnosed anxiety problems & I believe severe depression. This is a problem everyone is ignoring. I can't do it anymore. I don't know what to do. She's my sister & I love her, but she needs help. This past summer, my son confronted her about his missing wallet, saying, "you steal sh!+ from us all the time." We turned the house upside down looking for it. A couple days later, it showed up, in the middle of the kitchen table, minus $35. This all transpired into a major anxiety attack & her in the ER with high blood pressure diagnosis. This is why I hesitate to confront her. That, & I have no exact PROOF. She babysits my 8-year-old frequently, and my daughter adores her. WHAT SHOULD I DO? HOW CAN I MAKE IT STOP? Moreover, HOW CAN I GET HER TO ADMIT SHE HAS A PROBLEM SO SHE CAN GET THE HELP SHE NEEDS?