I think this movie has like three stories, and one of them is this:

There is a girl and she works at a gas station at night. It's her first night. She brings school work to die in the down time.

Anyway, all I remember is the ending where the killer terrorizing her ends up being her boss. In one part of the movie, she leaves the keys in her office or something. Also, the character may have been portrayed by a black girl, I'm not sure.

This movie was probably from the 90's, maybe even the late 80's.

Any help is appreciated, thank you.

Sounds like Body Bags