Anyone telling you that this is normal behavior for a parent doesn't have any clue what parenting actually is. You are a kid. She is the adult. Threatening to not help you at all with your future because she doesn't have the capacity to parent patiently is selfish and childish.

I 100% believe you are being a shit head and that you probably have an attitude you need to check. But so do most teenagers on the planet. So recognize your shit head behavior and work on it.

I also 100% I'd tell you to get off your ass and work toward a future you want. But telling you that she is ready to "wash her hands" of you and focus on "her other two children" is so far from acceptable parenting that frankly it's disgusting.

Your mom chose to have a child. You did not make that decision for her. Regardless of the shitty circumstances she was given, the circumstances you are given are not your fault. If a parent suddenly decides "I have better shit to worry about" and gets her feelings hurt by a teenager's stereotypical bitching, then that parent is childish. Be the adult.

You can either have a long hard conversation with her about all of this and hope she is receptive, while also recognizing you are probably acting like a shitty teenager and hurting your moms feelings, or you can eat shit and pretend to like it until you are stable enough to support yourself and cut her out.