Boundaries with Clients

I have a client that I have completed three projects for. She loved the first two and does not like the third one. Her behavior has turned to being downright rude. Her last message was “Let’s cut the losses, redo the project in this manner and send to me by EOB tomorrow! This is the end of our interaction.” My thought is to refund her money for the one project because to do it her way will not give her the result she is after based on my opinion and experience. My feeling is that, if I do this, she will create trouble for me and say derogatory things about my business. I have never fired a client. How do I maintain my sanity, keep my boundaries of not working with rude clients, and keep my strong positive reputation intact?