Michael was (still is) in the mainstream classroom, but we always made it a point to give him the special ed "option", so that if he was having an especially bad day, or was having a hard time getting himself under control - he would have someplace safe he could go to. We made it part of his IEP. All he had to do was tell his regular teacher that he needed to go to Mrs. Clark's room (or whichever teacher for that particular grade once he got into middle school) and they knew exactly what he was talking about and there was no problem.
Maybe your daughter needs a "safety zone" like that. She knows she's in the regular classroom, but if she gets overwhelmed, she can step out and pull herself together without the entire class watching her do it. You might speak to the counselor or special ed teacher to see what kind of accomodations can be made.