My wife was in a similar situation as a piano teacher. She was working 2 days per week but managed to get a B-permit. We also went to RAV but I wasnt very happy with the treatment and the options they provided. In fact we had to fight with them for several issues in the law that they were interpreting wrong. At least we won
For some professions (teaching I think is one of them) 100% is counted differently; its not the regular 9-5 , 5 times a week. Still 3 hours a week is too little... There is no way to know what will happen if she applies for a renewal since there are too many factors in place that we dont know about (how many permits issued so far, from which countries etc.).
I suggest getting another temporary job, even as a seller in a store in HB and then apply for a permit renewal. The more employment hours you have, the better. Once she gets the permit she can start looking for a job that suits her better. This has worked in the past.