Nikki, talk with your daughters' counselors and doctors, get their recommendations ............................... ie better for her to stay with the familiar right now and let them help her to deal with her brothers coming to you or to totally change her environment.
You say they know her, they have been working with her, and if it were me, I would go with their recommendations, ........................................... which I suspect will be to leave her for now with your folks .............................. where she will get 'one on one' with both of them, and be seeing the counselors and doctors she is familiar with. It will be hard for you, no doubt, but for your daughter may be the best thing, for now.
Please talk with her counselors and doctors. I am sure they will certainly give you their honest suggestions and diagnosis since you are her mom and you only have her best interests at heart.
I also think that CPS will look favorably on you for doing what is best for your daughter right now.
J M H O
Love and hugs,