I see what you're saying and I agree that Abbie is a major handful. But a major reason that she's like this is because A&P have been so lax and lazy when dealing with Abbie (or rather, not dealing with her) and now this is the result. They've done this to themselves.
I think any child would be like this if you didn't bother to discipline them, set limits, be consistent and follow through.
I don't know that it's too late to change, tho. It would just take some serious work and diligence and of course, A&P are not willing to do that.
THIS!!
Meltdowns are never pleasant to deal with. But, the longer you put things off to avoid them, the worse it will be.