Office jobs aren't a good choice either, because no office in these days needs someone to sit quietly with minimal public contact and sort papers and type a little. Those kinds of jobs went out with the IBM Selectric. She definitely needs to be working with the Vocational Rehabilitation department in your state. They will help her with a sheltered environment and possible training in some type of work they believe she is suited to do.
They will provide her with a job coach if she does get a job, inform the manager or supervisors what they need to do for her to help her succeed and will help her with on the job emergencies and problems. This means mother doesn't have to step in and do it all for her. It also means she gets a lot more support and evaluation from people who may be able to help her figure out what kind of work would be best for her, so she doesn't have these bad experiences.
I'm fairly bright and not at all given to shyness or panic attacks, actually was more confident as a young person, but the restaurant work I did was some of the most challenging I ever had. And the lower level managers and supervisors at restaurants tend to treat their employees worse than anyone else. Why do you think they turn over staff so often and hire just about anybody? The basics of the jobs are simple to learn and require no higher education or professional skills, so anybody who wants to try can come in and try, including the management jobs, you see. Those managers aren't going to be the best either. But being awful to people who work for you and with you isn't illegal unless it is done outside the letter of the few employment laws we do have in this country.