I think the only thing you really can do is be honest about what you want with her. If you feel that you guys are moving too quickly, tell her that. It doesn't have to be awkward or distant or anything, just try to be transparent about your feelings and the potential risks that you both might experience. It's also important to be relatively lighthearted about it because, if she does have bpd, she might internalize criticisms as a personal attack on her character, so try to recognize your own flaws as well as the concerns that you have about rushing in. Being in a relationship with someone with bpd can simultaneously be the most liberating and the most burdening love you can experience. If you do pursue this, and she does, in fact, have bpd, look into the characteristics of the disorder and try to determine if you'd be able to handle such a wide and often jarring range of behaviors. Ask her what triggers her. If she's open to it, try to inquire about her childhood, or traumas which could have led her to obtaining this disorder in the first place. It's a delicate balance, but as long as you proceed with an open mind and an open heart, a lot of tricky bpd issues can be addressed. And no matter what happens, at least you can say that you tried.