There's just different levels of care! (Customer and animal!) I wouldn't sell any of my birds if I had even one sneezing or looking poorly. Last time I was at aberdeen mart there were some sneezing and with weepy/closed eyes, it's a disgrace.
And scaly leg mite - do people actually think this is ok? I've not been to an auction yet and not seen birds infected with this. Sorry, rant over.
I'm sorry your birds are dying/not improving. I hope you can return the lot for what you paid, and get an apology and her word more aren't getting sold till they're all healthy - although it's hard if she's a friend... Live and Learn I guess?