It is so frustrating when you get two different opinions about what you should do.
Did you ask the emerg vet if her prednisone dosage would be higher if she was not taking the Imuran? I have never had a dog that required steroids but it is my understanding that if Imuran is given then they can give lower doses of prednisone.
Hopefully, Dr Lee will reply soon with his opinion.
Glad her appetite is good
and sending you lots of