Well, Mary didn't actually attack her physically.  She made her claim as alpha cat, and everyone complies.  It's better than it was.  Just wait and see how things progress.  Sometimes my alpha male wants "that place" all to himself, and sometimes he'll share.  Sometimes, I think he's being a jerk and just shoving his weight around, and sometimes he invites one of them to curl up with him.  As long as it doesn't get out of control and no one gets hurt, that's progress.  It's when the bullying goes on and on, like with Bingo, or between my alpha and my black kitty, Ziggy that I lost last January, that it's a bigger problem and more difficult to stop from happening.  If that has lessened with Mary's presence, then Momma having to give up her window seat sometimes is worth daughter Bingo not getting ulcers from constantly being physically harassed in earnest.  Just a thought...