aww sorry to hear you are going through it at the moment, it all seems to be piling up for you
As the others have said, make sure you get help for yourself as well as cookie, dont let them put you on for with a doctor thats not compatible with you at the moment, try asking for another one at the practice if you dont feel entirely comfortable with the one they keep giving you. sometimes a fresh approach with a different doctor is all thats needed to kick start the healing process for you. A different angle/perspective is often all thats needed to start putting pieces together again

(maybe look at the Surgery's website & see if the Drs have a timetable on it, pick a day when the usual Dr isnt in, will save you having to ask for a different one, if its awkward for you)
i'm not sure how cavvy savvy your vet is.... but £110 seems excessive for an ultrasound, my Ellie had one for ovarian cysts about a month or so ago & they didnt charge me more than the consultation fee this time, dont remember for sure, but cant remember her charging for the first ultrasound either, but if she did it wasnt much.... definitely not that much anyway

mine are not an exotics vets & generally well priced, but thats just crazy pricing!
could you try a different vets? or even double check with the vet that they got the price right if you want to stay with your current vet?
***Ellies ultrasound consisted of 45 seconds worth of belly hair clipping, 10 seconds of squirty stuff application on the scanner & about 5-10 minutes max of looking around on the scan for all the important bits& checking what was going on. then another 30 seconds of squirty stuff being removed with a soft cloth. i held her throughout & had a good look at all the process going on

I dont think they can justify £110 for that.
Good luck with the hand feeding, seems like you have done it before so that's a bonus!

i think sweetcorn is a food that helps with weight gain short term, they can eat the corn, green husks/leaves &cornsilks (stringy bits that go up through & poke out the top)
introduce it gradually i usually do about 1/4 a day each for mine they love it. dont know if it does them any good to feed it in large amounts long term, but it should help to get the weight on now whilst she needs it.
Did you try
@Kerrie74 's link for financial help, sounds like you could do with a boost
Take care of yourself & make use of any help that you can get.... A happy healthy you, is a start towards a happy healthy cookie too.
Keep us updated & please have a look through other members links they have posted for you, they are a wonderfully, helpful, caring bunch, with a vast amount of knowledge.
Big hug for you & hope things start looking up for you. Take care. luv Ellie, Grace & I. x