She used the gas, so she is responsible for it. If she doesn’t pay it, she saddles the former account holder with the balance and that sucks. She never asked for the service to be put in her name, but if it were off, she’d have no heat. (How someone could not know what kind of heat they have in a house they BOUGHT is pretty incredible to me.) It’s wild to me that you or she could think there’s any other answer besides “pay the outstanding bills for the service I used and get the account switched to my name.”

If there was an outstanding balance when she closed on the house, nothing before that date is her responsibility. After that, though, it is.