Yes Melanie (((( Hugs)))) and
We had similar with DS2 due to severe reflux. He developed a severe oral aversion and was wasting away before our eyes. It was terrifying.
In case any of this helps you, I'll pass on the tips that got us through.
Don't ever try to do things the way other people do or follow their weaning plans or judge yours against theirs. Your DC has very different needs and the solutions may well be the exact opposite of typical good advice on healthy weaning..
The most important thing is to get the highest possible number of calories into each spoonful. DS would take 2 5ml spoons of food a day. We used to mash up avocado with banana, as 2 spoons of that was equivalent to half a pot of something else.
Don't worry at all about giving 'unhealthy' food. The most important thing is to get her to like food, to enjoy it. Try sweet things, and textures she doesn't yet associate with food. DS would chew on a cream cracker coated with cream cheese and jam. He wouldn't eat it but some would go in. Or he'd try ice cream. Those are both dairy but you could try non dairy ice cream or get her tested for peanut allergy and if she's OK do PBF toast or PB and mashed banana. Don't expect her to eat it, just to chew or suck on it. Add sugar to purees, or a drop of olive oil - anything to pack more calories in.
When she's old enough try baking a very high protein cake. I made up a recipe of soy flour, almond flour, lots of eggs and sugar. You could use non dairy marge instead of butter. He'd eat a mouthful of that a few times a day. (Though maybe not at eight months.) It's crumbly and melt in the mouth, but you'd need to check on egg and almond allergies first.
One thing I did was make up pots of tiny bite sized pieces of food and carry them round all day, popping them into DS's mouth when he was playing and not aware food was going in. Wholemeal bread with dairy free spread cut into tiny I cm square sandwiches or those Organix Noughts and crosses which are quite high fat irrc.
At mealtimes I only brought out treat foods - ice cream, biscuits, anything he'd willingly eat. This was to get him to associate sitting up at table with pleasure. When he was watching TV or playing with toys I'd just tuck miniscule morsels of healthier food into his mouth all day long. This really helped. he'd never sit down and eat what his friends would eat but over the course of the whole day if I 'posted' all the time, enough would stay down to keep him alive.
Don't worry about sugar and teeth. Their milk teeth don't last and sugar is an appetiser that makes you crave more. In emergency cases like this, that's a good thing.
It was a VERY slow process. He was absolutely tiny for years. He ate the same food day in day out for about eight years. We worked out that as long as he had something from each major food group it didn't matter what it was. When he started primary he was still bald with baby hair and wore age three grey shorts as trousers because they went down to his ankles. He's now tall as me aged 12 and really well built and loves his food.
Sorry this is so long. I just remember how tough it was. Hardest time of my life and I wouldn't wish it on anyone.
I really hope things work out for her and for you.