This will work on basically any girl. Whether you know her or not. When you see her, make eye contact. But then look at her shoulder or hair, a place that she can't clearly see herself and put a straight look on your face and say "OH MY GOD. DON'T MOVE, THERE'S A BUG (WASP, SPIDER) ON YOU". Then act like your trying to catch the damm spider and lets say it moves around so you get to touch her for a bit and then you "catch it" and "kill it" or "let it go free". make sure she doesn't get a chance to see what it was. and then look her in the eyes and say with a confidence & funny voice "yuppp i just saved you life, no need to thank me, but (dinner, coffee, etc) would make us even". Make sure you say all this was a smile/smirk on your face otherwise it's gonna be a fail.

That sounds a bit too direct to me. Shouldn't there be negs, kino escalation, etc. before you go in for the close?

it doesn't need to be that complicated. but sure those things would help