Facing burn out over a student who doesn't want to improve

I have a teen student (F) who I've been working with for a little over 2 years now. Though it has never been disclosed to me by her parents, I have picked up on the fact that she has some behavioral issues and is most likely on the autism spectrum. Not a problem for me at all, but I do not have the ABA training that would probably be beneficial for her.

We schedule lessons weekly, but I've been finding myself wanting to cancel more often than not because of a lack of commitment on the student and family's part. It is clear that she does not practice whatsoever throughout the week. She has learned her note names very well throughout our time together and can read and play melodies well. She also knows basic chords. However, she refuses to play with two hands because she says it's "too hard". I have done everything in my power to simplify it or break it down for her, but she refuses to even try. When ask her to play something unfamiliar, she often refuses. I have bought her 3-4 songbooks, only for her to not want to play anything out of them.

From what I've witnessed, she treats her mother the same way she treats me. She doesn't listen when reprimanded and has to be told to do things 10 times over before she listens at all. I know that her family is not encouraging her to practice or stay consistent. I am starting to feel burnt out, and also think that my time could be better spent with other students who are more committed. I feel this student may benefit more from somebody who can be there to do musical exploration with her rather than the formal lessons that I offer. She's a sweet girl and she's emotionally attached to me on some levels, so I would love advice on how to approach this respectfully to her and her mother.