Old shepherds would have referred to that as the ewe 'trying to put her lambing bed out'.
There is a tendency for prolapsed ewes to strain as if still in labour; there are a couple of methods for preventing her from putting her bed out; she can have stitches in her vulva, or you could insert a prolapse 'spoon' (a plastic object which resembles a uterus with its two horns) which is inserted into the vagina and tied to the wool at either side by way of bits of tow through the eyelets in the 'horns'.
If she does manage to put it out in the meantime, you must wash it well and try to keep it clean as it is re-inserted, before giving a dose of long lasting antibiotics.
On a sheep farm that ewe would be marked for culling.