Awww don't feel like you have to leave. We try to ward buyers off of bringing pups home at 8 weeks because it is better for the pup to stay with the litter/mom until 12 weeks. However, that doesn't mean we are going to run you off with pitchforks and torches if you end up with a pup that is 8 weeks.
Another reason to ward off people from buying them so young is that, after some more digging, sending them home so young is often accompanied by other "red flags." They tend to indicate a "greeder" or in worse cases mills. Often, selling young is an early sign that it is not somewhere you should purchase from. Note: I said OFTEN not ALWAYS. However, it is extremely often.
Ideally, you want someone that adheres to all the reputable standards as a breeder and that includes someone who waits until at least 12 weeks to send them home for the well being of the pup.
I would encourage your breeder to keep him if you can, but if she refuses... If I'm being honest and I were personally in your situation, I would probably take the pup anyway and cut my losses. I would NEVER purchase from that breeder again, but I don't think I'd have the heart to leave the pup either.
You'll have to put in extra time and energy to make sure your pup grows up happy, healthy, and socialized. As long as you are up to the challenge though, it isn't insurmountable. You'll have to take extra care teaching your pup things like bite inhibition, and he'll be extra tiny and more susceptible to certain things. Just do your research and become aware of the problems you could run into and prep for them.
We'll be here to help the pup if we need to be. It isn't like we're going to shun you both.
