so we had our relationship going for 5 months and i noticed that she had a lot of mood swings, at first I thought that it was normal but it started to get on my nerves because she could go from being happy to being depressed in a matter of minutes, some days ago i found out that she was cutting her arms and I asked her why did she do that and she got mad at me, she told me that I never gave her the attention she deserved tho i always tried to understand her. 
I spoke with her parents and they told me about this BPD thing.
Right now i dont know what to do, we have really good moments and our relationship works, but there are things that are really starting to affect me personally and i dont know how to tell her that i dont want this anymore.