Hi K..
I am 34, and I have 3 kids. My daughter is 11, and my sons are 8 and 5. My situation is a little different because my husband died 5 yrs ago, but as I read your post it felt eerily similar.
My suggestion is to get her help. My daughter has gotten increasingly worse as she gets older. We resumed therapy this school year. If nothing else, therapy holds them accoutable for their behavior. My daughter tries to make me feel guilty about it, but the common thread with the therapists is that my daughter is highly manipulative. Sometimes they are too smart for their own good (or our good)!
I have heard the same lines from my daughter. "You don't love me, You ruined my life by having my brothers, Nobody listens to me, You just don't understand anything, My life sucks, It sucks to be me." The list could go on and on.
I hate to discourage you, but things will get worse if an intervention is not made. Therapy does not make things better quickly, but as I said before, it holds them accountable. The biggest thing that has helped me is to just ignore my daughter when she starts screaming, and to stick to my guns on things. Don't give in!!! It is soooo hard, but it is so necessary. There are times where she screams for an hour, laying on the guilt, crying, etc.
My problem is that for years I felt sorry for her because her dad is not here, but I wasn't doing her any favors...or myself! They need the discipline. Unlike your situation, I was the fun parent, and my husband was the disciplinarian. This past 5 years has been quite a struggle for me because of that.
My daughter is really smart, and she asks a lot of questions. I would find myself explaining everything to her. We don't owe them an explanation on everything. It is so hard to remember that.
My daughter has a terrible time with the fact that I have a boyfriend. It boils down to a competition for my attention. She is always asking who I love more, and she tries to put me in situations where I have to choose. I have stopped discussing things with her that we have gone in circles with for some time. I just tell her, we've been through this, I'm not discussing it anymore, and I walk away.
It is really hard for me to be like that, but it has helped. When she screams or goes into one of her rages, I tell her to write it down in a letter because I'm not listening to her when she is like that. They need a mom, not another friend right now. They know we love them, just like we know they love us. They just need reassurance that no matter what, they are number one and you will never leave them.
Eleven is an awkward age anyway. They are turning into young women, yet they don't seem to fit into a certain category. They are too old to be with the little kids, but too young to hand with the teenagers. (My daughter has started her period also, and while I think hormones can play a role in things around that time, I do not think that is the sole reason for our daughters' behavior).
Good luck! I feel your pain. Stay strong, and stick to your guns!
L.