In my honest opinion, therapy can be awesome for everybody and not just people struggling with issues.

That said, if she truly is dealing with BPD or some other issues of a similar nature and you truly want a GOOD and HEALTHY relationship with her that will be longstanding, then I would absolutely recommend that couples therapy be an absolute MUST for the both of you.
Therapy for her to help her help herself and therapy for you to help YOURSELF so you can both help her/support her through this AND make sure you stay mentally and emotionally healthy throughout the process.
It may not sound romantic, but having any kind of disorder - even if it's purely medical like managing something like longterm diabetes - is hardly romantic at times and is best healthily managed by being honest and open and willing TO manage and cope in the best way possible... . at the get-go and not down the line.
Working together as a team - you, her, and a good solid therapist and/or other healthcare professionals - gives you and her AND the possible relationship the best shot possible by starting off on a positive foot forward.
All the best of luck to you in whatever you choose.