Back story I am deeply in love with this woman we have been involved for about a year and a half she has left me multiple times in times of rage and come back and we start like everything is amazing again this last time was the longest with about a 2 month gap where she entered in to a somewhat relationship with a different man but before going to far she again came back to me 
Writing this out sounds like a creepy stocker guy post but she has bpd and I understand that this relationship was going to be different than I ever had before but shes worth it we also are currently in a long distance relationship being about 20 hours away in different states my hope is that someone here could help me understand ways to better support her and keep our relationship strong while she fights the demons she has
Thank you 
TLTR:asking for advice how to support my girlfriend with bpd and keep our relationship strong