Oh I'm sorry for you have no advice really hope you spread the word around bout that breeder though, he should have never sent you home with a bird that wasn't ready like that. Your bird should have been eating well on her own, this should never have been an issue for you.
Sounds like you are doing the best you can though, great job bringing her to the vet and hand feeding though.
So glad my breeder was not like yours, I was so impatient.. at 8 weeks I was dancing sure I could bring Windy home but he week after week he kept putting me off, at 12 weeks he finally gave the ok.
At the time I was so frustrated now I'm so grateful I never had to live through this experience.
Best of luck to you and your baby... lots of good people here to help you who have excellent knowledge about this though so I'm sure it'll work out well
PS I'd definitely try the almond in the formula as your vet suggested..
