97 Jetta - not starting

Ok here's the deal. My friend owns a 1997 VW Jetta, that won't start. She left her dome light on, so the battery died. She went to jump it and the guy who was doing it, said she needed to replace her battery, so she did. Now the problem is, her car still won't start. The AAA guy she had look at it told her it was the alarm's ignition kill that was preventing us from starting it. He said that the car was confused because of the key and it thought it was being stolen so it was cutting off the ignition. So we closed all the doors, locked and then unlocked them manually with the key. When they locked the alarm beeped like it was activating and then we unlocked it so it was deactivated. The car still does not start. So my question is, what could be doing this? Why won't it start, and what can we do to get it to start? Thanks guys for any help y'all provide!!