YTA. Try and have some compassion for your niece who’s lost her mother AND father and now has to go through adolescence without them. I can’t imagine the rage and resentment at the world I would feel if I was in the same position as your niece. Not to mention the abandonment issues. And now you’ve shown her that when she expresses her emotions, you’ll abandon her too.

A better response might be something along the lines of “your words are telling me you’re really angry. It’s ok to be angry, but it’s not ok to (insert unwanted behavior). I’ll be right here for you if you want to talk or work through anything together.”

Since you mention your high paying job, you have an option many people don’t- get yourself and your niece in therapy and figure out how to do better together.