She just loves her mommy, it's just separation anxiety and makes us mommy's feel horrible for the rest of the day. They usually are fine within minutes after we leave. Has she made any friends, this will help a lot. Time is the real answer, just tell your friend to be strong and just remind her that mommy will be back after school to pick her up. It's just a little scary for her, she's so young, their are big kids there, she's use to being with mom. Maybe mom can go a little later so she doesn't have to be in the gym early, not that she's late for school, but maybe being dropped off closer to when it starts, only a suggestion, sometimes that isn't an option.
Good luck,