1997 Chevy Cavalier

My daughter has this vehicle at college. After driving 150 miles she stopped and shutoff car. Then came back out and drove about a block and car quit. Tried to start (it turned over but no start) She said that she had a 1/4 tank of gas. I told her to put in at least a couple of gallons to make sure there was gas in it. After her and friend did this they didn't try to start immediately, food was more important, came back in 20 minutes tried it and it started. No problems for couple of weeks driving almost every day. Then she said she would start it and it would want to kill but kept on gving it gas and after a while it would start to sound normal then she would procede. She came back home and I took it to my mechnic at local car shop. They ran different tests and of course could not duplicate problem thye changed oil and fuel filter and ran alternator load test
but since it would malfunction they did'nt suggest replacing the fuel pump. Is there something else that could be a place to look.A friend said maybe its the oxygen sensor another said something about a emc or emg fuse or relay. The other day she drove it from work 2 blocks to get coffee worked fine drove it 5 minutes later and it died. Pushed it into parking lot finished her work shift and came out and it started and drove home just fine. I'm 150 miles away and can't just pop in and check stuff out. Thanks for any help!