hi ds2 had really bad reflux, only went off the meds when he was 2yo, despite many people telling us 'it'll get better when he sits up/starts solids/stands up/[insert your own developmental milestone here].
However, once he went on omeprazole it helped him a lot, so it's a pity your dd is not responding well to it. I think kids can respond differently to the different proton pump inhibitors (of which omeprazole is only one) so maybe it would be worth the docs suggesting another one?
Also is your consultant a general paediatrician or a paediatric gastroenterologist? With ds2 we were only seen by a general paediatrician on the NHS but we decided to pay privately to see a paediatric gastroenterologist. He pretty much agreed with what the general paed had said, to be honest, but we were reassured that if there had been anything else going on he would have picked it up. He did also say that our son was probably in the worst 5% of refluxers which was kind of reassuring in that he acknowledged there was a problem and we weren't making a fuss out of nothing.
We definitely found ds2's reflux was variable and got worse when he was ill.
I agree with the comments about possible intolerances as that's often linked with reflux. You really have to watch out with soya as many kids who are intolerant to cow's milk develop a soya intolerance too (as did my ds1). (Oh, just noticed that starshinetiger said something similar.)
Anyway, as soon as we realised he had a soya intolerance as well as cow's milk, my ds1 just stopped having any formula at all (and he had already weaned off breastmilk). I can't remember exactly how old he was but he was eating loads of solids, so we weren't worried about calorie intake. We found many ways to ensure he had a good calcium intake, like giving him calcium fortified orange juice, rice milk on his cereal, lots of eggs, bread, hoummous, apricots, broccoli and so on. Your dd may be a little young for this but you do say she's eating well, so I just wonder if the soya milk is really necessary? Kids do vary so much though: with ds2 i just kept breastfeeding him as long as possible and expressed enough for carers to feed him from a bottle. And, in contrast to ds1, he took a fair while before he was taking much in the way of solid food, so I wouldn't have felt comfortable reducing his milk intake.
Have you found the PAGER site yet? www.reflux.org/. They have loads of good info and some very experienced volunteers so you could contact them for advice.
Another site I found useful was the MARCI-kids site www.marci-kids.com/, from a US research group looking into PPI meds used on children. There's good stuff about how children metabolise the drugs faster and so they need higher doses per kg than adults would. I seem to remember the info from here also made me decide to give the omeprazole more frequently than the paediatrician had suggested, and it made me aware that the timing of the doses was important too. I think the omeprazole works best if you give it half an hour before food (although I can't locate that info on the site at the moment). They do however seem to promote Zegerid, which I don't think is available in the UK.
Finally there are loads of people with good advice on the infantreflux.org message boards and the Yahoo! breastfeeding reflux group.
Sorry for the long post, just trying to remember stuff that helped us even if our situation wasn't quite the same as yours is. Thinking of you. It's a tough thing to go through.