He had legal access to them, but didn't have her permission to take all of them.
I was afraid of that. The same thing happened to my grandmother and there was nothing to be done. She should probably contact whoever is holding outstanding checks from that account and make alternate arrangements for payment because putting mire money in to cover them is potentially a never-ending spiral of suck. if she can go to them and say "That check I gave you will bounce, here have a money order instead" she might be able to close the account quicker.