I agree, do not bring her to meet your sick mother. You can't save her from herself only she can do that.
Maybe time away from witnessing her chaos will help you understand that this is not a healthy relationship for you to be in. 7 months and you fell hard for her and got sucked in with her childhood gone wrong story.
When we witness and feel RED FLAGS while dating someone, that's the time to slow it down, step away so that we can view the big picture of it all.
Try and focus on your mom and being there for her. With you or without you present in her life she has and will do drugs and that's a fact you can't change.