If you getting a dog is a deal breaker and all the other issues that seem to arise from the illness she has then is this something that you really want to live with long term? Life is hard enough without all that other drama.
She needs to take care of herself and if she is to have any real long term progress she needs to want it and set boundaries herself. Maybe if you both had some time apart you would see how how committed she is to maintaining her own wellness.