Gee this sounds familiar...

Been there, done that, but don't have a souvenir T-shirt to show for it. And I broke the cycle by not having children. Drastic measures, I know.

What I can add is only that unfortunately your older daughter grew up with the preception that that sort of treatment is to a certain extent "normal." I'm not saying she's a lost cause, but it's hard to break the cycle. Continue to a positive support to her, but make certain that you take care of you. Try not to cut the boyfriend down too much, that may chase her away, but to point out the positive things in her life. Lift her up, but don't put him down.