A good breeder knows their lines. They will when the sell puppies know which ones that are good to hold back or sell as potential breeding stock and which should be sold as pets.
At six months, they will see stuff that they like or dislike in a dog, and they may have a good reason to want to breed the bitch, from what they see.
It really depends on the breeder. It may be that the breeder just takes it for granted that in another year or so when she is ready to be bred, there might be some reason at that point not to breed her, and that could be disclosed then.
If the breeder is willing to do all the rest of it, including helping with finding buyers for the pups and that is what you want to do, and you trust your breeder, than I really don't think that is the worst think that can possibly happen. There are worst ways to jump into breeding. There is no evidence that the breeder would just slap any old dogs together. It depends wholly on the breeder.
As for getting a bitch pup because your bitch is lonely, please do not do this. Young bitches can HATE each other, and they can cause you a lot of grief. Have you considered looking at your local pound or shelter, or a local breeder for an older male? If you go ahead and neuter him, he will likely get along great with your female and no chance of an oops litter.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC