I couldn't agree with daryl more. My youngest are twins (now 16) and for the longest time people thought that they had to treat them like a package deal. I think limiting Bug to do things that only Crash can be included in will cause resentment by Bug and a sense of entitlement by Crash. Children are very clever beings, they pick up on the sub-text very quickly.

I hope her father gets on board with the program very quickly. As long as Crash sees that her tantrums are doing what she intended they will remain a very effective tool for her. As long as they're effective, she'll continue to use them.

My eldest has/had a very severe case of ADHD, this is not an excuse for bad behavior, medication will not solve that issue. Medication will simply give her a few seconds to decide IF she wants to act that way. Watch a few episodes of Supernanny, it really is as simple as changing YOUR behavior. Don't get me wrong, changing your response is difficult, and she'll continue the behavior until she realizes that you (and hubby) will not respond to it anymore.