We have these things already. =)

User shops contain eggs for sale. We each have our own hatcheries already. Pets for sale are in Rancher shops, and each user has four free cla.ss changes that can be used to switch from Merchant to Rancher, so you can decide which you like better.

XD mirrors, I think she means pets for pets. I can't think of anything else but I know neopets had something like this (and many other sites too I just can't think of any because it's way too late at night and the exact phrase "pet pets" makes me think neopets XD). No, I am not saying anything about it being like neopets, I'm just using it as one of the many examples of what she might mean.

Anyway, on to the actual suggestion. I don't like this idea very much personally. I never liked the thought of pets having their own pets, it's just odd and doesn't happen. They can have friends, but that's entirely different. Humans are the only species (that I can think of off the top of my head) that actually keeps "pets" so having a pet keep pets is just... I dunno.

Anyway, enough ranting, I'd have to say no on this one.