Was it said if she'd ever been to raccoon city before? I'm guessing she had been cause she seemed to know where the police station would be to meet Leon so she might have stood a chance, but then again she entered the cafe and spoke like she was new to town. but either way, without Leon driving her so far and without the handgun, how far would she make it in the streets? even if she got to the police station she would die at the train cause Leon wasn't there to start it.
Really tho she would have most likely got back on her bike and rode out on the seemly empty, safe street she came in on.
Sherry would get raped by her dad as usual but this time the embryo would kill her. Ada would get shot by Anette without Leon there to take the bullet and she would bleed out or anette would walk over and smash her face in.