By what you have typed, she's getting scammed. DO SOMETHING before she give them anymore money, What sounds like happened is they you fixed the maf, didn't clear code, You thought the light would go off by itself, it won't, you took it to dealership, they are scamming you. DO SOMETHING. End of story.
EDIT: Also have her tell the whole story to corp, even bring up refusal to get a quote and not signing to authorization for them to fix it. Scotts right Gm would have no problem having it done at no charge to customer.