I have a 17 year old daughter who is a junior in high school. Her dad and I are divorced.
If you were my daughter, I would be very proud of how strong you are. I would want you to go to an Al-Anon meeting. I have cried at those too. It's a good thing, it's a safe place to cry.
You have your whole life ahead of you, I can see that you love your mom, but truly, you are not at all responsible for her behavior. And it can hurt you so much. You deserve to enjoy these special high school years.
Sending hugs and positive thoughts to you.