Hi. We don't know where you live, so what you're finding may be a factor of your individual school district. Guidelines for placing students with special needs into the Least Restrictive Environment apply for Kindergarten to 12th grade, but I'm not sure if they apply to Preschools. Unfortunately, at any grade, there usually are guidelines for the kinds of assistance that regular teachers can be expected to provide for an individual child. In regular classrooms, they do expect children to be able to take care of their own toileting needs. Where exchange of bodily fluids is likely, or a teacher would have to leave the rest of the classroom unattended in order to assist your daughter, schools are understandably reluctant. In a special class, there is usually a lower teacher:student ratio.
I don't know if a 1:1 aide would permit your daughter to function, but you might request one on her IEP for when she enters Kindergarten.