That happened to me years ago in EY. I don’t think she was unconscious; I think she just hurt her leg, but I don’t remember the details.
I happen to be terrible in emergencies, but I went to the nearest payphone (this was many years ago), figured out the number to call for emergencies (I think it was listed on the phone) and called. I then waited with her until the ambulance came.
I went to Shaarei Tzedek on Shabbos to try to visit her but couldn’t find her. So I guess she was okay in the end. I remember it was Shabbos (when I tried to visit her) because I remember the way the receptionist reacted when I got nervous when she started looking the name up in the computer and I told her it wasn’t necessary. She laughed and told me that she’s a goy.