Pictures would help - :)
Could be a mild allergic reaction to something (mine are already acting up) - does she eat out of a round bale? Any changes in hay or bedding? how/where is she kept?
Or is it more like her eye orbs are swelling, causing the area around her eyes to bulge out? In which case, I'd call the vet asap personally.
Trying to think of other possible causes, but where it's both eyes, it does not seem likely that she bumped them both on something...