Yea that's all good but she isnt the restaurant manager. She didn't hire him and It's not her job to evaluate his performance.

If the person in charge the kitchen says "can you stop recommending this dish" and the waitresses says "nah i think it's delicious, im going to keep doing it" then that's just messed up.

Front and back of house are supposed to be a team working together.

They obviously have no respect for each other.

If someone wants to order a meal 5 mins after close the wait staff will ask me if it's OK first. Even though I'll almost always say yes. They ask out of respect of my position. Because it's my decision if i want to substitute/cook off menu/cook after hours.