2000 Toyota Corolla sometimes stalls when pulling out into traffic?

My daughter's 2000 Toyota Corolla has been stalling when pulling out of the driveway. She revs the engine when she starts it before backing out of the garage but by the time she gets to the end of her driveway and starts to pull out onto the road it dies and she has to restart it. We have had this problem off and on but it seems to be getting worse. She took it to Sears and had them do a tune up and flush the fuel line. It seemed better at first but now, after a few months, it's worse. I bought a bottle of fuel injector cleaner and put in it but that didn't help either. It doesn't do it every time she goes anywhere, just sometimes. We traded her cars for a few months and didn't have much trouble with it. It might have died once or twice but she says it's doing it a lot to her now. I'm wondering if it's a sensor. Is there anything else it could be besides a sensor? I also wondered if the fuel filter needed replaced but my husband thought she would have trouble all of the time if it were the fuel filter.