Whether she was acting as a police officer or not, she could and should have backed out of the door and called for backup. IMHO, the fact that she is a police officer makes it WORSE: she had the training and moreover the equipment to deal with the situation rationally, while a frightened civilian would not.
I think that the statement was just poorly worded and “adverse conduct” is meant to refer to the actions that caused her to be arrested for manslaughter.
I also think that firing her is a clear signal that the department administration does not support her.