I can't stand my disabled sister any longer

I just can't see her without being filled with absolute rage. She will do anything for me and my mother to be uncomfortable. Noises, clapping, nose picking, hitting walls and the floor (we live in an apartment), nasty stuff like peeing over my mother's hands when she's changing her. I just can't deal with it ANYMORE. Just because she's disabled she can act out, lash out and be angry. No one really knows how hard she can be and i'm fucking sick of hearing ''oh she's overstimulated'' ''oh she's stressed''. She is NOT. She gets fed by hand, gets whatever she wants handed to her and we constantly play servant for her. I'm 21 for fucks sake and i can't do anything with her nearby.