The Brady Bunch was full of shit

Is there any such thing as a truly blended family? One that is happy and one in which everyone is equal? Or is it always a struggle? I used to think we were one family. I used to think we were happy. Now, I don't think anything will ever be good again. The saga of Ch has been well documented here. I thought we were moving past it. But it seems we will never be able to. Carla says it's my fault. But in reality, I cannot say anything to Ch anymore without being accused of "having a tone" or being a bitch. I've basically been told that I am not allowed to say anything. So I decided to just cut her off. I said I wasn't doing anything for her anymore. Why should I when all I get for it is an attitude or criticism? I fought to get her help with her education. Now I'm told that I shouldn't worry about her grades. That I just want to "gloat" over her failures. What Carla doesn't understand is that it makes me sick to see her grades falling in the toilet when I know that if her father did what he needed to, she wouldn't be having so many problems. And Carla doesn't seem to care. I wish I didn't. Even with me saying that I wasn't going to do anything for her anymore, I find myself still doing stuff. I wanted to buy something else for her birthday. I bought a cake mix to make for her party. Yet, I'm constantly accused of not caring. I DON'T WANT TO CARE ANYMORE. So every 2 weeks, when Ch is here, we go through this. Me being accused of being a bitch. I honestly don't see it. I asked about her grades, and got attacked. Yet, every single day, she verbally beats up on J. He can't look crooked without her saying something. When she gets up in the morning, the first thing I hear is her yelling at him. Can he be a pain? Yes. I don't pretend like he is perfect. But he doesn't act any different than the other 2. He can't let things drop. He has to keep arguing. But so do the other 2. I understand that a biological connection is stronger. I don't expect her to pretend like she doesn't love her own kids in a different way. But why is it okay for her to treat him that way? I hate it. Why can't she see how much it hurts me? I really just wish Ch would just stop coming. It pours salt in an open wound. And the only way she seems to deal is by verbally battering me. I know that Ch is her daughter. And regardless of what she says, she hasn't dealt with or gotten over the fact that she left. Nor do I think she has moved past the fact that she feels responsible for that on some level. So once again, I get the blame. It's easier for everyone to blame me. I don't claim that I am perfect either. Do I get snippy sometimes? Yes. The hurt often manifests itself through anger, directed towards Ch. But it's not constant, like I am accused of. I don't even think it's often. I guess I sound selfish. I don't think, though, that this 12 year old should ruin what could be. I just wish I knew how to fix everything. It takes two though. I can't fix it alone. And sometimes I wonder if there is anything left to even fix.