She is not ready for school if she is crying and throwing up for 3 months I would advise that she stays home till she is older, what is the school like are they good, do the play , read, stimul;ate the children how long do they sleep during the day. Ther is a reason she doesnt laike it, she also may be having some seperation anxiety form not being with you .Keep her home for a while then try just a few hours a week till she gets used to it again and take a look at the school and what activities do the children participate in . ..Good luck