I am new, so I am not sure if I have the best advice; but I would just simply neg her until she leaves or stops talking. If she comes up and starts blathering like a buzzed little attention monger, call her on it.
Here are a couple example of "calling her on it" - I am willing to take advice too
When she starts talking, lay your head on your shoulder or back and snore loudly (with a smile on your face of course) like you fell asleep. She will giggle and make some reaction to that, then start talking again,. Just do that over until she says something like "oh, fine, i'll let you talk"
When she starts talking, just give her a nasty look, but in a joking manner....so that she thinks you are joking, when you really are not
When she comes over, ask if she would be interested in meeting some other people. When she says yes (which she is going to do - loves attention - thats why she won't shut up), you GET UP from where you are at *this will help isolate target, if you are not already isolated* and say they are over here. You grab your HB9's hand, and guide her along with you to point out a couple people for the HB7. Walk up to a group, introduce the HB7 and as soon as she opens her mouth to do a greeting, you walk away with the HB9.
or, if you don't care to close at all with the HB7, ask her nicely to socialize with someone else; you are trying to have a serious conversation about *insert something you know the HB7 would not be interested in*
With the third scenario, that will also give you some more Kino with the HB9, isolation ability, and (even though you said you did not need it) social proof. You are also turning into the nice quy trying to entertain someone who you were not even obligated to help!
Again, I would put these out as tips, but they are not tried nor true.