I would be a little leery of a breeder who gave me 1 day to make a decision, especially with them all being so young. I also prefer to deal with someone who insists on raising the pups indoors, but that's just me. Did she mention why she was in such a hurry to have you select your pup when it's only 4 wks?
Is she breeding just to sell the pups or is she planning on keeping any of them for her breeding program or to show...because IMO it's way to early for her to even decide which ones are show prospects or even be aware of their potential.
I really don't know anything about Minis (I think Tulip is our resident expert here) but it's not all that uncommon for a Mom, to not look her best (hair loss, borderline thin) I would ask how old she is and how many litters she's had (as well as how often)
Does she show/compete with the parents? I'm assuming she doesn't compete or title her dogs if they are living in a stable. Does she have photos of her looking her best? I'd also want to wait to meet the sire before being forced to make a decision.
Did she provide you with referrences from the kennel club or from others who have purchased from her in the past?
Has she given you permission to contact her vet?
Does she give you a health guarantee?
Does she have a contract?
Have you checked to see if she has infact done the testing on the parents?
I didn't know you were looking for another dog, Sarah...exciting stuff
I bet Synnu will be delighted to have a playmate.
Take your time and be cautious. Just try to remember that no one should push you into making a decision so quickly, that you may end up regretting. I wish you nothing but the best in your search