if she is legit BPD, her behavior won't stay stable. She may not rage now, but something small will set her off to severe depression or mania.
I dated one for 8 months. Starts off very needy, tries to wear you down over time, will never get over their men issues, tend to lie and mislead a lot.
Eventually found out she spent last month sleeping with another guy and me at the same time. She dropped him and begged me to stay with her but I threw her to the curb. Said she was just filled with so much rage towards me (and I never did **** to this girl, I treated her great, you will never be treating them good enough though) that she did it to hurt me. Beware as these kind of behaviors are normal.
Drugs and support will not fix them, their broken for life (if they are legit BPD), no joke. Pump her and dump her, or you'll end up regretting it.
EDIT: and the guy who said she will emotionally rape you is right. I had never in my 23 years EVER been depressed or self loathing until I met this girl. She dragged me into it so ****ing deep. Thankfully I rebounded to my old self as soon as she hit the curb.