I Have Issues With My Mother

So every few months or so it seems that I have to rescue her from some ridiculous situation she should have never been in. Throughout the last 4 years she has moved in and out of my house, oh... about a dozen times. Sometimes she doesn't have money and I have to send it to her, each time she swears up and done she is staying with me. I've bought plane, trans, and bus tickets. I've bought her cars and had to turn around and sell them, sometimes not even a month later. I've missed work to drive up to 20 hours to go get her, one time we ran in to an avalanche (good thing I'm one of those weirdo preppers).
This last time she stayed the longest... I told her that was the last time...my boyfriend says it's the last time...

She abused me physically, emotionally, and verbally as a child. As far as I am concerned I owe her nothing...
Yet, I don't know how to tell her to piss off.
I cannot have a life with this continuing to happen.
This is not healthy for me.
I liked it better when she stopped talking to me...

She called a few days ago and said she wants to come back to my house.

I wouldn't let anyone else ever treat me like this!