It could be that she is itchy, or hot or any number of things.
It's also the season for mares to start coming into their first heat - being two this would probably be her first ever heat cycle and could be very painful/uncomfortable. This could explain the excessive sweating and rolling.
My mare came into heat very suddenly when she met my new gelding, within a minute of touching noses with him she had dropped to the ground and rolled and just lay there biting at her belly. Got up and pawed like colic. It passed after a few minutes.