Quite honestly I think you did awesome. With my daughter, 7, we send her to her room until she decides to be nice or happy because no one else needs to suffer. And since she can’t stand being alone because she gets bored, it works swimmingly. We also keep her room for sleeping. All her toys are kept in the living room or in her closet where we can hear if anything is being played with. It’s almost like she needs to reset. As far as your little ones siblings go, don’t try to explain her behavior away or reasoning for her behavior. Even with good intentions, this may cause resentment. Call it for what it is and don’t explain it away. If the behavior was selfish it was selfish. Not because she has ADHD or whatever and address it appropriately.