I get exactly how you feel, about being between childhood and adulthood. But I'd like to answer your two questions, if I may...
There are things in this world that you cannot control. Yeah I get it but does that mean I have to like it? If I don't accept it, is it called denial?
No and no. If you don't like something about life, you do not have to accept it and when you don't it's not denial. Denial would mean pretending that you like something which makes you miserable. If you don't like something, you should always work towards change, no matter how impossible it seems. I hate to say it, but this is your life. Not your mother's. It's unfortunate that she's suffering from an illness, but it shouldn't be up to you to be her nurse. Especially if she is abusive towards you and you want to do other things with your life.
There are things in this world that you cannot control. Yeah I get it but does that mean I have to like it? If I don't accept it, is it called denial?
No and no. If you don't like something about life, you do not have to accept it and when you don't it's not denial. Denial would mean pretending that you like something which makes you miserable. If you don't like something, you should always work towards change, no matter how impossible it seems. I hate to say it, but this is your life. Not your mother's. It's unfortunate that she's suffering from an illness, but it shouldn't be up to you to be her nurse. Especially if she is abusive towards you and you want to do other things with your life.