I have just spoken to a different vet on the phone and she agreed with the first one, that most of the SR is absorbed in to the system so not much passes through. She reckons that as long as "something is passing through" then there's no immediate panic. When Bramble had the same problem he was pooping ok once he had the science recovery but he was eating lots of veg, he only went off the dry stuff. I know everyone is saying 120ml of food a day but i suppose it depends how much its watered down. I've been advised off the CCT that one packet of SR a day is advisable for an average sized pig, the packet is 20g. This seems to be keeping her weight stable at the moment. I'm keeping it quite a thick mixture as it's supposed to be better that way to avoid too watery poops so this means its less in mls. I just wish Gabbi would start eating more hay, I'm sure she would pick up more quickly. I'm wondering if she's missing her cage mates but the vet has told me to keep her seperate incase its a viral form of pneumonia. It must be quite a shock to be used to being with all the others then being taken in to the house on your own 
Poor Gabbi, here's to a speedy recovery.