Yeah she was in the living room and my older cat was in her room, so there was no reason for NC to tell her "to back off". I don't know why she attacked OC, but it's a big reason why we are still weary of leaving them alone together.Yeah, I agree with you that the behavior at the gate wasn't great. Sometimes cats will do a little charge/swat that is a backoff signal rather than true hostility, but probably its overly optimistic to count on it being that. Well, maybe going slow here is for the best. Just too bad you'll lose progress when you go, but at least you have experience with how they act and can better put everything in context when you come back and resume.
Do you have any tips on getting NC to stop thinking of the master bedroom as only her territory? Currently, she is in that room all day and sleeps there every night. She also has all her meals at the door there, while OC eats her meals in the living room and sleeps either in the second bedroom or living room. I think sometimes NC gets defensive when OC comes to the gate looking into the master bedroom.