If it were my sheep I would:
remove the ewe from the rest of the mob and confine her in a place where you can control her feed intake. I would also reduce the hay and very slowly start to feed her some whole shelled corn or grain, no more than 1/4 pound per day for the first four days if she isnt already on grain. I would slowly increase the grain to offset the decrease in hay...no more than a 1/4 lb increase over the course of 4 days. It is too late in her pregnancy to put her on a diet to actually lose weight, by doing so you can risk ketosis, but you can reduce the bulk in her diet (hay) which is causing the pressure on her.
Short tail docking + fat sheep + lots of hay = prolapse.
When you use the twine harness just remember that the key to how it works isnt by the pressure it exerts on the vulva but rather the pressure that it applies to the top of her withers. When the pressure is applied to the top of the withers it causes her to very slightly hump up and she can not push down on the partial prolapse when slightly humped up. This is the same way that those "hot bars" work in the old cow dairies to keep cows from peeing over the milking attendant. If you gave her a shot of nuflor and washed her up good, I doubt that is an infection that you are seeing but rather vaginal secretions from the irritation of the "spoon".
If she is showing signs of swelling around the spoon, you may want to lighten up on the tension.
Also...if she is pushing it is because she feels the swelling and it greatly helps to reduce the swelling which you can do by washing the exposed area gently with warm water that has approx 1 TB of vinegar added to one quart of water (apple cider vinegar is my favorite choice
By this means you are cleaning off the debris without causing further irritation to the delicate tissues and ACV is a great sanitizer when properly diluted.
After washing, then liberally coat the swollen area with clean granulated sugar,( the sugar will help to draw out the excess edema, like sugar does to strawberries)
Once the prolapse is replaced, then use the acv water dilution to sponge off the vulva of any excess sugar. We do not have flies here at the moment, but if you do, you may not want to use the sugar....if you do have flies and use the sugar, make sure to use a fly repellent around her tail area.