just checking - is your daughter's Magsafe adapter a 60W version? or does she have a MacBook Air and it's corresponding 45W charger?
your MacBook needs the 60W (or higher) to charge the battery. if by chance you're trying to use the MacBook Air's 45W charger, it might run the MacBook but not have enough power to charge the battery.
if you're not using a MacBook Air charger, then ignore the above - it would be some other problem.