take the bike and say this :
' fock of wh0re now i got a nice free bike of 23245 dollar (or something) ...i don't wanne **** u for 3 dollar cya motherf*cke
I'd stop, perk an eyebrow, then focus ahead and keep on going.
If she follows - then I'm obviously going to have to address the issue. It is, however, my experience that there are strings attached to good things that simply drop into your lap. A girl determined to strip in front of me would be one such thing that I'm going to expect to have strings attached to it.