I think also that she is trying to cool herself. All out dwarfs are sleeping out in the open just now, usually lying on their backs
You can give her a ceramic tile which has been put in the fridge to lie on or even just the tile is cooling. Also a terracotta flower pot on its side can be cooling. Keep the cage in the coolest area of the house and shaded from any sun. Have a fan in the room but not directly on the hamsters and you can offer a slightly defrosted veg such as a frozen pea or a piece of cooled cumcumber (only a tiny bit though) Dwarfs have very thick dense coats and can have trouble cooling themselves. Make sure they have plenty water.