My gf has no sex drive... please suggest some medication... she is 25?

Mismatch: "sex drive" is a subjective thing. What we often find, especially when we here this from a partner, is that there is a "mismatch" between the expectations of one partner and those of the other partner. These are almost always psychosocial issues and not medical problems (although there are some medical issues and medications that can affect sexual interest). I suggest you start with talking.

No magic medication: There are many reasons for having "no sex drive". Depression, anxiety disorders, guilt, shame, conflicts in the relationship with you, all could be possible reasons. There may be physical reasons -- pain during sex, hormone imbalances. She needs to be evaluated by your family md or if you suspect emotional problems then a therapist needs to be involved.

Not so fast...: Have you ruled out medical problems, side effects of medications, drugs/alcohol? Is she experiencing stress, anxiety, poor sleep? Are there relationship probs? Kids? Is she tired from work? Does she have a history of abuse? Is her low libido new or chronic? Would your girlfriend be interested in seeing a couple's counselor? I would address all these issues prior to seeking medications!