And what friends are they if he/she does not know how abusive is your ex?
Honestly, how could any one know? I think the severity of abuse can only be appreciated by the one who is going through it. My view is if you like the friend, don't think too much into the future. Just continue to date and feel it out. Keep a healthy distance and boundary. Be a bit guarded and figure out how deep their friendship is and see if her friend is also a PD. I mean, it is not like all PDs get together and make friends. So there is a good chance that she is not. Also, I don't think people who are PDs like to be with people who have PD. So chances are, she may not have it. But you should still be guarded. If you and your new found relationship grows into something, there is a good chance, she would have to choose either you or your ex. Or she can understand the situation and work with you to keep a healthy distance and maintain boundary.