I don't think anyone was thinking that you don't do stuff with her hun. We all know you're a great mumma. I just think it's that she has higher attention needs than the other two, and acts out accordingly. She's found that hurting and being mean to the others makes you come to pay her attention, albeit negative attention. But if she's getting into trouble, then I guess in her mind the other two aren't getting attention, kwim? And it's possibly just the terrible twos.
DS is going through it now and pushes me to the end of my tehter. It's making me tear my hair out becasue DD never went through it. DD was pretty bad at 3, but it has gone now and she's back to her normal pretty thoughtful little self. But DS just tries stuff to push buttons. I see him glance at me before he does something he thinks will get my back up, then the look of 'mischevious' on his face when he does it and I get cranky at him. He's just trying out what he can do and what he can't but by god he ****s me!!!
Have you tried not paying her attention. So if she lays on E, pull her off, turn your back to her and pay all of the attention to E, and get A in on the act too if you can, you know 'Poor baby, are you ok, awww, that squashed you didn't it, come on let us(as in you A and E) go play nicely together.' Then M needs to apologise to E for hurting her, and she can join you when she's going to be nice...You have probably tried it....but hey thought I'd try to make a useful suggestion!