Hi there
As a vet, I would think that there are a couple of potential reasons for sounding like having a sloshy belly.
Firstly, if she is getting close to lambing, they can have a condition where they produce excess birthing fluids, and so would have a very large, fluid filled uterus, with a lamb somewhere within it, which may slosh a bit.
Another reason for having fluid in the abdomen would be a loss of protein from the blood, causing fluid to leak out of the blood vessels as there is too little protein to trap it in the vessels, this can be caused by heavy bouts of diarrhoea, or fluke damaging the liver, and with her having had a green bum and having been treated for worms and fluke, this is a potential.
There are other things that could be going on, but I think the most likely from her history would be the second option, that she's lost some protein, but you've done the treatments required - ie worming, fluking and taking off the grass in case that's caused the scours. As long as she's eating, drinking and looking comfortable, I would just keep an eye on her. It may be that the sloshing sorts itself out, or it may have to wait until she lambs.
If she goes off colour, off her food, off her legs, or anything else unusual, I would get the vet to take a look, otherwise I think a bit of TLC would do her just fine.
Hope that helps
Suzanne