I have a number of rental properties and have the accounts moved from the tenants names to my own from time to time. Somebody at the utility company screwed up big time if they allowed a new these changes on HER account without HER approval. Give them a call. She can insist that things be put back the way they were before they added to her account without her approval.
They made a big mistake and should be happy to, at the very least, put thing back the way the were before the unauthorized changes.