You've given good tips here that are universal. To the letting go and delegate I would add, don't micromanage what you've delegated, but also don't make the person feel like you have just thrown them into the deep end of the ocean either. Help them navigate until they can swim on their own.

My immediate thought upon reading your comment, "Nancy would talk about her terrible team ..." was Uh-Oh! How did that toxic person get to be  manager? Thankfully you didn't catch it.