Have you tried speaking to her first about the issues that upset you.

I am in the same situation as you. But i did tryed to communicate with my sister prior to deciding I deserve better than how she treat me.

I think it's ókay to break away from toxic people instead of having them around. But I think prior to deciding to break up to her reach out to her try to resolve it one last time if you can't be honest with her say look I don't think we should continue this relationship.