What is wrong with my 1994 Chevrolet Camaro?

My girlfriend has a 1994 Chevy camaro. A few days ago she left a plug in heater on and the battery went dead. After giving it a jump in the morning, she drove it to work. On the way home she was complaining that the car was sputtering and stalling out while she was driving. When she got home I took it for a drive to see what she was talking about. When i started the engine the car revved up to about 2100 rpms and then sputtered down until I pushed in the throttle. I drove it down the road maybe a mile to advance because I thought maybe it was the fuel filter. There was a half a tank of gas when I drove it to to advance. Between there and back the gauge said I used up a quarter tank of gas in maybe a mile and a half of driving. When I got home I replaced the fuel filter and started the car up but no luck. Someone told me to check the fuel pressure to see if the fuel pump went bad but it wasn't that either. I decided I was going to take it to a shop but when I went to start it today it started up, began sputtering and died like it was doing. But this time it wouldnt start back up. There is no milky oil, no smoke coming from the exhaust, no leaks in the fuel lines, and she just had the mass airflow sensor changed a couple months ago. Any ideas on what it could be?