Understanding the Borderline Mother by Christine Ann Lawson is a book that I found helpful -- not perfect. I think one could go further than Lawson did in understanding how a "borderline" person feels about herself, and why. There are other helpful books too. You might look up the subject on Amazon.

I Hate You, Don't Leave Me is supposed to be good too.

Now, about helping such a person, maybe if she read some of the books herself and identified and thought that she was not beyond help...

Maybe you could read some of those books and leave a book that you thought was good around the place for her to "find"...