This isn't necessarily directed at OP, but I have never understood why guys who are 25+ get so hung up on a girl's lay count. Chances are if she is 25+ she is going to have at least a double-digit lay count unless she has been strictly in LTRs her whole life. I would venture a guess that most of us are really no different.
If she has a reputation as a true slut that is a little different -- but I think that is a rarity.
While I understand and agree on both sides, I think girls that's slept with a lot of dudes(relative figures to various people) by a certain age could signal other things about them: insecurities, low self esteem, lack of learning from their mistakes, no self improvement, bad decision making, lack of good judgement, lack of standards, etc.
This does not yield a quality gal in majority of the cases(there are exceptions of course). If you decide to embark on a LTR with one of these gals, it could affect you in negative ways. For example, if she lacks good judgement, she could put you in financial ruins if you ever get married to her for example.
We often blast guys on here for making the same mistakes(letting gals take advantage of you financially, attention wise), it's no different than gals that keep making same mistakes(in this case, just freely sleeping with anyone). Everyone makes mistakes but some just refuse or are incapable of improving themselves and their situation. That's the difference and it will show and manifest itself in other areas of their life.