I guess this may better be answered by an SO who has experienced this situation but I think you need to give your gf some time with this and, perhaps, have her get some counseling with you or separately from you by a gender therapist who can help her make the decisions she needs to make. Her world has been turned upside down and the pictures she had of your future life together have been destroyed. I think she will need some time, maybe alot more, to regain a sense of stability in an all too suddenly uncertain world.
It's good that you can still talk and that she can ask questions. My wife went into shock for a number of weeks and wouldn't even let me bring the subject up. Let your girlfriend assimilate this new information and try to be patient, as impossible as that may sound right now. For her sake, rush slowly.
hugs & smiles
helen