The only way I'd leave an injured friend (male or female) alone on a trail known to have had muggings and other assaults would be if the friend was so injured that they couldn't move and I had to go for help. Otherwise, I'm sticking with them until they are safe. Or if they tell me, in no uncertain terms, to go and leave them alone. They wouldn't have to *ask* for my help, because I would just help them.
One time when I was hiking with a friend, we cut our hike short because we encountered two other hikers, one with a broken leg, trying to get back to the trail head. Sure, we could have continued our hike, but instead we turned around and helped get the injured guy back to safety.
Of the 4 women in the group, Stacy seems to be the most "social" runner and the least interesting in improving her time or distance.
And there's no reason for her to be upset that Kelly drove herself to the hospital instead of waiting for the other three women to get back to the parking lot.