Dont ask her to do anything more than introduce you to any girls she knows. You will come off as desperate, like they said above. Also, girls are horrible matchmakers. They will ruin your chances, and make it seem like they are trying to pawn you off, which is unattractive. You would have to train a girl to be your wing if you wanted this to work.
This is what a girl would do, if she agreed. She would introduce you, and tell the other girl what a NICE guy you are, and how lonely you are, and how you deserve a good girl, and blah blah, blah, thus making the girl think you are a total nice guy, wuss bag, loser.
A good wing-woman would do the opposite. She would casually tell her girlfriends that you are SOMEWHAT of a heartbreaker, and that your other girlfriends were/are super hot, and you broke up with them, because you felt they were using you just for really great sex, and you need something more after three months. She would also bring up your strong points in other womens presence, like "Hey Kal, I forgot to ask, how is {insert attractive hobby, accomplishment or quality here}. For me it would be, "When is your band playing again?" or something along those lines. Then, girl would be interested, and want to know more, and you can tell her a little bit about it, without it sounding like bragging.
Using me as an example again:
Wingwoman: "Hey horaholic, when is your band playing again?" turns to her girlfriend, "Have you seen his band? He is a really good guitar player, and looks really hot on stage. lol" then you act all modest about it. Target is now interested in you.
"setups" dont work, but good wingmanship can work very well, if they know what they're doing. I've told my friends to come up to me, while Im talking to a girl and shake my hand, and tell my how good my band was the other night. It totally works. Its almost better than the girl actually seeing it live, because they can use their imagination. Its DHV'ing without saying it yourself, and sound like you're bragging.