She's not taking the pup home yet ... just getting dibs!
I think 6-8 weeks is probably prime. (That's when we brought our first one home. We had picked him out when he was 2 days old.

Clearly, we had no idea what we were doing. But it worked out.)
We went to see Ozzie's litter at 11 weeks -- and came home with him. He is as much a lover now (at age 10) as he was that first day.