Students and young, inexperienced directors can take criticism personally and get very defensive. It seems to be even more of a problem as the 'there are no wrong answers' generation gets older.
Heard a pro football coach say that he made sure that players knew he was 'attacking' (his word) their football character - not their personal character. I used this to start every year. Understand that I am going to criticize your playing/marching. I am not saying anything about you personally. I am going to say, "That is out of tune." I am not saying, "That is out of tune - I'll bet you hate kittens." The goal is to fix the musical/marching error, and we all make errors. Yes, there are times where personal character (behavior) needs to be addressed, but that will always be from a position of giving you the opportunity to fix the behavior.
You need to adapt this for your colleague.
What is the best approach to give constructive criticism/feedback to a coworker who is super sensitive? This co worker is not the world's best teacher, knows this, and is extremely conscientious and sensitive about it. This coworker also snaps at me, uses sarcasm, or personally attacks my teaching if I try to mention a way to help fix the show (they are in charge of a struggling section). At our contests, when the score is low, this teacher says the judges were wrong. Yes, seriously.
I have tried the compliment sandwich, I've tried light, breezy conversation about "what if we tried this?!" type stuff, etc. Not working.
How do you fix weak students when this teacher takes offense to "interference?" I know I am not a perfect teacher, but I really want to make this band be all it can be.
For what it's worth, this is between two assistants near in age and teaching experience. I am trying to figure out another option besides "go to your head director." She can't make the other director receive help more easily. She actually told me "you know how he is, just let him be." So...yeah. I truly want to have a good teaching environment, but also get our scores up in this section. Any advice is appreciated.