K.S.
Ive noticed with my son and with some other kids in my life that when they start out of nowhere having "seperation anxiety" at that age it is usually for a reason. My friends son (3) was in preschool for a while then one day begged her not to leave him. He did this for weeks before they found out that some kids had been teasing him ruthlessly. Once that stopped...he was fine. On the extreme side, my sister when she was 4 started begging my mom not to make her take naps at the baby sitters. Turns out the babysitters 14 yo sold had been molesting her during naptime. With everything in child rearing..."Better safe than sorry". It could be that another child is calling her names...this is very difficult for little ones to handle too. Another mother had suggested dropping by the school- I think that is a great idea. Good luck.