“Shut up and go to sleep,” said one of the boys as they passed by. (Why would they tell her to go to sleep? That seems out of place.) She looked like a cornered animal, ready to strike out at anything that came close to her. Denise noticed the girl because she had shared a class with her in high school. Denise thought her name was Amy. (New paragraph) Crouched on the ground with her back against a large stone, Amy had beads of sweat on her forehead. Her hair was matted and dirty, like she had been rolling in the dirt. She was crying and clutching her jacket as if it were her lifeline. (was she wearing the jacket or just holding it?) Her eyes were wide open, she was frightened by something Denise couldn’t see (sentence structure). Feeling sorry for Amy, Denise kneeled down next her to try and help. Amy turned and glared at Denise as if she were waiting for an attack. Denise carefully stretched out her arm and touched Amy’s cheek to wipe away a tear. The action was met with a shriek and a backward lunge that caused Amy to bang her head on the rock.
Critique: Watch your grammar and sentence structure. This is a little choppy. You jump from the boys, to Denise, to Amy, back to Denise, back to Amy. It didn't feel smooth to me. You might consider changing to a first person POV with Denise. ??
Would I ask for more? No. It just didn't speak to me. Sorry.