I think you should just talk to the teachers about it. Ask that they have her sit on the potty at regular intervals until she is back in the habit of asking to go. I think this is normal for preschoolers, so it shouldn't be a big deal for them to have her go at certain times of day.

My 3 year old attends preschool 2 times a week from 8:30-1:30. She suddenly stopped asking her teachers to go to the potty after she had her first accident. She is now holding it all day. What can I do? help!