I am pretty sure the battery is dead, because you mentioned you used it for a couple of days without charging and then it went black, It was probably an older battery to begin with, so letting it completely go dead was the straw that broke grandmas back. The other clue is that it seems to charge and then kicks off. it wont do that if the connector is broken

The battery is toast, they need to get a new one.

What State and city are you located in?