That is wrong. There are only roughly 20 restricted jobs. She is Music therapist, so: obviously she can work in that job.
She can not work as bus driver. Thai massage specialist - unless she is a physio therapist - then she can, sculp buddha sculptures, and so on. There is actually a LIST of restricted jobs, which you can google. And list got cut from roughly 35 to about 20: YEARS AGO.
If you are a specialist: you can work in what ever you want. Provided you find a job or make your own company.
If you are really good in Music and like to try: I would try to find a school, e.g. an international school, and become music teacher.
Regarding the other comments: you do not need a lot of money to found a company. They are mixing up registered capital with "upfront costs", yes you need a Thai partner, 51%. Depending on province more than 1 partner.
Yes, one can work as a chef. No idea why the nay sayers are so uninformed. However bus driver is a restricted job. And no: you also can not drive a cab, bolt, gap etc.
The husband can be a cook. You are silly. He does not cook Thai dishes, but foreign dishes, facepalm. Or do you think the French and Italian restaurants or Indians are Thai cooks?
You can find a sponsor on site. But depending on some other rules, you might have to leave the country for a few days, and apply for visa in an embassy outside of Thailand, and then come back. But - most of the time it should be possible now to do it without leaving.