I think Camille knows that her relationship with Amma is codependent and that she’s not just taking care of her because of “kindness”.
She’s not Adora and wouldn’t hurt Amma, but she definitely “needs” her in a way that goes beyond simple sisterly love.
Camille is a very lonely person. Her boss and his wife seem like lovely people but when they are your only friends that’s not a great spot to be in. Amma gave her a purpose. A reason to clean up her life. She now has a sister and a best friend again and even a daughter on some level. It’s not surprising at all that someone in her position, that has gone through what she’s gone through, would go overboard and maybe willfully not see what’s right in front of her because she doesn’t want to.
She doesn’t seem to have put Amma in any kind of therapy, maybe because she doesn’t want to learn that Amma is mentally ill and beyond her help which might get her taken away. She also hasn’t stopped the sleeping in the same bed thing. When she tells Curry about it, she doesn’t seem upset or overly concerned. It’s just a fact of life. On some level she probably doesn’t want it to end and would rather let Amma stay a baby or little girl for as long as possible.
I haven’t read the book, but if I had to guess, Camille would be just as likely to set that dollhouse on fire and burn the evidence as she would be to turn Amma in