Hi Ophelia,
You have my deepest sympathy. Reflux and FTT was the hardest thing I've ever had to face in my life - I ended up with severe PND. Ours wasn't over until he turned 4.
But it does end. Now he's 10, a really solid, muscly rugby player who adores his food and cooking. Until he was 4 he barely ate enough to live. When he started school he was almost bald with that translucent baby hair and he wore age 3 shorts was trousers, he was so tiny. People used to gasp when he trundled into the hall at assembly. Just telling you that even if it is severe and she doesn't grow out of it for ages - it isn't forever, and it doesn't have to mean any long term ill effects.
Best tip I was ever given, (by another mum) which no medic suggested, was to feed them straight away after they've been sick, just give a new feed, small amount. Instead of following standard feeding patterns, do little and often. I fed DS2 every hour. Keep her upright as much as possible. We never did 'tummy time' because he was in agony, so he sat up in his buggy or rocker as that stopped the pain. He even slept more easily in that position. We were shown how to burp him on our laps, rather than against the chest, as the pressure on the stomach can cause vomiting.
We were told to move onto solids asap and feed them almost continuously in minute amounts. I used to tuck food into his mouth while he played because if he didn't notice it, he was more likely not to refuse it.
Allow more treats than usual - I offered lots of biscuits and ice cream because it was so important that he learned to equate food with pleasure and this was the only way i could think of.
Also, offer full fat yoghurts, add cream to purees etc, so that even if she arches and screams after two spoonfuls, you've given five times more calories in those two mouthfuls than if it had been healthy stuff.
As long as she tolerates something from each key food group, don't fret about variety. My DS lived for years on nothing but soft brown bread, mild cheddar, yoghurt and slivers of peeled apple. Once I finally knew it was habit not physical, I got tough and now he's less fussy than DS1 who ate everything.
Sorry, this is really long. I feel so much for you. It's vile, But it will pass.