D.P.
try a couple of half days to get her used to it. linger around a little bit the first couple of days and make sure she has some kind of transition activity for the morning: play with a special toy, read books, etc...make sure to bring a special toy or lovee that she can hold on to if she is nervous, pack something special in her lunch...
she will probably cry the first couple of days, weeks...but she will adjust and be fine.