As long as she's H-O-T and does it in a string bikini. (kidding)

Seriously, women have worked on my car so there's no reason that I wouldn't want/trust them working on my bicycles. Presumably if they're wrenching in a LBS she's been vetted to prove she knows what she's doing. But, I do all my own work on my bikes so it's a non-issue for me (IMO shouldn't be an issue for anyone really).

Dan