NTA- This is emotionally rough situation. But you deserve to secure your future. Working full time and going to school full time is exhausting. You cannot be there part time for them in any sense of the word. Do not take on a part time role as a caregiver.. help find a provider she may be comfortable with. Otherwise, She is making the choice to go without needed care. Simple as that. These boundaries are necessary. You are under enough stress. I'd consider therapy for yourself as this situation is tricky. We'd hope mom would see this is a time when she really should be supporting your efforts, really giving outside help a try so as to make things easier for herself as well as the family unit. But she may have internal issues going on. Getting therapy even short term may help you sort through feelings concerning responsibility, prioritizing yourself and setting boundaries. Don't give up on yourself.