I don’t know if this has been said as I’m having to skim read through rage but it proves that she didn’t get the kitten from a legit place, because rescue centres don’t send out tiny kittens that two weeks later vets say should be pts. Where was it Jack? Gumtree? Facebook marketplace? Ad in the newsagent window? You should be ashamed
Definitely, it was a friend or some casual arrangement. Cats Protection for example would never home a cat like this until the vet treatment had been completed (and if it was a long term disability, they’d only hone to a foster with specialised experience and the means to see to the cat’s long term veterinary needs).