Aww it looks like cherry eye to me. How old is she? My female Blossom got her first cherry eye when she was 5 months old, and we fixed it at the same time as we spayed her at 7 months old. Then a week after her surgeries, the left eye came out . We thought we were well and clear for the other eye, because it was 3 months apart, but no such luck, so 3 weeks later we had the left eye repaired. We opted to have the eyes stitched back in, rather than taking the eyelid out, and have had great results for both eyes. . If she is still young, and this is the first time the eye has come out, you may want to wait a little bit to see if it goes away, sometimes it does. The only thing I would suggest if it does keep coming out, is to buy some refresh eye drops, and place them in her eye to help the eye from drying out , because when the eye is exposed to the air it drys out, and gets irritated which causes swelling. A trip to your vet might be a good idea, to see if it is cherry eye, as I am only seeing a picture, and could be wrong. He can give you recommendations as to what you should do. Good luck, and keep us posted.
Here is a picture of Blossoms' cherry eye