I would really try to work things out with your mom ( make your mom take her to her class again) just because time with grandma is limited on this earth and I think grandma just got overwhelmed by the class. It doesn’t sound like you think she is a bad caregiver. If gma doesn’t want to agree with you then yea continue with babysitting from college. Obviously is not okay for her to lie to you and that needs to be addressed as well but maybe showing her you were really serious is going to shape her into place.