This happens.
It is common.
The Teachers are used to it. It happens every year.
A child, will adjust.
It is life.
The book "The Kissing Hand" is good. About going to school. Can be found at any bookstore. Real cute.
Ask the Teachers, how they handle the kids who cry.
So that you know, for yourself, how they manage it.
So you can feel better.
It is an adjustment. And since she had never gone to a "class" before.
Keep in mind, that after school, a child is tired or over-tired... they had a full day at school. It is like 'work.' They need to come home and deflate. Unwind. And even nap.
A child will learn, to self-manage.
Concentrate on the positives.
That each child is different. So that she does not feel she is the only one.