Girl guns is a term that can make a guy very unpopular with the ladies.
My definition is what they shoot best with, and like to shoot the most.
My experinces have been, the ones that every lady has shot and liked were.
1 Heritige Rough Rider .22 lr, or Ruger Single Six they all love to shoot them probably for the same reasons I do they are just fun plinkers.
2 Colt Python .357 mag 4 inch bbl. every one that has fired this one loves the feel and acuracy of this one. (many have tried to talk me out of it, none have succeded so far)
3 S&W 4906 9mm Currently it resides in my stepmother's gun purse.
4 Ruger MKII (this was my grandma's she was deadly accurate with it) perfect for arthritic hands, and women with osteoperosis)
5 S&W M&P 45 full sized (my sister, stepmom, girlfriend, and several other women love the ergos of it.)
6 Bersa Thunder 9mm UC (my girlfrieds EDC she loves it, I carried the .45 version for 5 years, she shot it and liked it just got the 9mm version for cheaper ammo so she could shoot it a lot more)
7 P64 9mm Makarov (my girlfriend loves this one, and shoots it very well, we have one on order just for her. Mine rides in my front pocket.)
So it all boils down to wether or not she will actualy shoot it. If a woman does not like to shoot, or is otherwise not entusiastic about shooting it realy does not matter it is going to go in her purse or in a safe, or nightstand drawer not to see the light of day very often if ever.