Confused

Girlfriend's Ford Contour 1996 won't start. I put the key in and try to turn if over but the battery was way drained. The battery was kinda corroded. That would indicate a bad alternator but, she said she had tried to jump her car and it wouldn't jump which could mean a bad starter. Anyone have any ideas?

It would be easy to see if its a bad starter. You can hear it or you cant.