Never ask questions that you don't want the answers to. How do you date a friend's ex girlfriend? This is Doctor Paul, author of "Boomer Girls, a boomer womans guide to men and dating", and host of "Ask Doctor Paul". It's doable, lets start with that, however, don't be intrusive. The woman has chosen to date you for whatever reason, if she is dating you in order to get back at the friend that you have, that may have dumped her or maybe she dumped him, that can be a tenuous situation but lets say that that's not the case, they just chose to agree to disagree and now you are there with her. The worst scenario ever is to ask her about their relationship, you may not want to know, it may be T.M.I. (too much information) you don't want to go there and she may be uncomfortable in talking about that. The best way to approach that is say "look, I know you dated my friend, I know you had a relationship and that was between my friend and you, this is a new day, that door is closed, this is between you and me so we don't want to talk about that ever, not now, not in the future, never, not a factor, not a point of interest". She will feel far more comfortable with that and so will you, so keep that one in mind, it is doable. This is Doctor Paul, may your fantasies of today be your realities of tomorrow.