Oh gosh, it sounds awful, poor you.
I would 100% follow your instincts and take her back to the hospital. I think you could reasonably ask them to make double sure she doesn't have pyloric stenosis or some other digestive anomaly like a hiatus hernia etc.
If this is all clear, then explain that the ranitidine is not working, not even at max dose, and ask to try a PPI drug. Omeprazole is one, but the easiest to administer IME are lansoprazole fastabs, which are dispersible. They need to be given on an empty stomach (or as empty as possible) and 30 minutes needs to elapse between taking them and having next feed. Tricky but might be worth it if it works.
So, the LC and paed said that trace things in breastmilk is likely not the cause of issues (and I am sure they are right, it is perhaps unlikely) but not impossible. Sensitivity to cow's milk and soy protein was suggested as the cause to my baby's woes by my LC so it seems they don't all have the same beliefs about that one. Is it worth one last shot of cutting out ALL traces of dairy and soy for a couple of weeks to see if that improves things? I know it's really, really difficult and another thing to deal with with all this going on....When I was in your situation, I didn't do the dairy exclusion but in retrospect really really should have (as DS turned out to have a significant dairy allergy along with reflux). You and your babe might well eb different but I thought it worth sharing!
Yes there is a reflux support thread, or there was.... it was in breast and bottle feeding. I will see if I can find it.
You mention not knowing how to cope yet. Well, I think it's important to realise that parenting a non-reflux baby is a completely different experience to parenting one with the condition. It is about 1000x more difficult. I don't think this fact is appreciated enough by paeds and family GPs who just tend to bung you in the 'new first-time over-worried mother' category. If they could only spend 24 hours looking after your baby they would soon change their tune :)