She doesn't take suggestions well and then says the administration is not supportive of her. She appears to have given up on many of her students. I feel as if I am between a rock and a hard place. I don't want to have to replace her with three months of school left, but I also don't want the children to suffer because of her having given up on them. Dear Between a Rock and a Hard Place, You are in a tough position indeed.
Midyear replacements are never easy on anyone, particularly on the children.
You seem to have tried several different options without much success. This is one possible approach. I would schedule a meeting with the teacher, preferably after school so that you have time to speak to her without interruptions. Be honest with her and express your concerns. Try to focus on the major issues since you might overwhelm her otherwise.