MUST HELP!?!?!!?! My mate wet herself at dance!?

Okay so today at dance cl we were leaning a new dance. The dance is ballet. We dont wear tutus, we wear leotards. We had to warm up, so we all got on the floor and did good toes, toes. For people who dont do ballet all it is, is you put your legs infront of you with a straight back and flex and reflex your feet sitting down. When we got up my best friends bottom was soaking wet, so was the floor were she had been sitting. My dance teacher is about 21 and she got her changed and told her mum about it.... what happened to her? why did she do this and she has never done this before?