Let me set the stage:
Anya sitting propped on the couch with a little toy ball between her legs. She has her hands on it. (It's one of those balls with another ball suspended inside with lots of pegs sticking out, and lots of little beady things in there, so they roll around between the pegs and make noise when you roll it) She's sitting kinda un-steadily and mostly leaning forward.
Ally is standing beside the couch "helping" Anya roll the ball.
Rob is supervising.
I am making grilled cheese.
Ally takes the ball away. Rob tells her that it's Anya's toy, and asks (tells) her to give it back. Ally ignores him, and Rob repeats himself. (You can see where this is going can't you?) Ally puts it on the couch and gives it a shove (passive-aggressive like. "If I have to give you the ball, HERE take it" implied in her actions). BONK! Right in Anya's face. SCREAM! SHREIK! AHHHH! Next thing I know, Anya is in Rob's arms, screaming her freakin' head off and Ally is sitting on the couch, crying her eyes out. Anya didn't even get a bruise (just a few little traces of blood in her snot that went away within 5 minutes), but it sure scared the crap out of me. Oh, the screaming!
Rob had to have a talk with Ally about expressing her feeling and not hurting Anya while she was mad at him. It was very obvious that was what had happened.
Is this what I should expect between sisters? It seems to me that I remember similar circumstances from my youth (at a little older age than these 2 of course)