Oh Rebecca, what happened to that poor baby is just completely and totally awful. Please tell your friend that I am so, so very sorry to hear about this. It truly does break my heart

That poor sweet baby...
I don't really know what to say as far as advice though. My friend got one of her Yorkie babies at 8 weeks and it did just fine - of course, he is bigger...so not sure if that had anything to do with it or not.
I'm of course not sure, and this is just my opinion, but I highly doubt the puppy died just because it was taken so young. I've heard of people getting puppies at 7-8 weeks (like I said, my friend got her's at 8 weeks)....some even 6, and they were just fine. To me - it sounds like this little one had an underlying health problem that it either wasn't checked for, or one that just went completely overlooked. Or of course, maybe it was just sick with, "something" and because it was so young - it's little body just couldn't handle it
Whatever the reason I am just so, so sorry that this has happened. It is so tragic, and so sad

I really do feel so very sorry for your friend. And I don't care what ANY vet says...SHAME on that breeder for selling that puppy at 7 weeks old!! There would have been NO HARM in letting it stay with it's momma for another 5 or so weeks. It makes you wonder if she just wanted the money