
My Rottie x GSD is nearly 4yrs old and she has never had a wee or a poo out on a walk as she just cannot relax enough. I actually prefer this though as it saves me having to carry a huge bag full of poo around looking for an elusive bin. I just let her straight down the garden when we get in.
My JRT on the other hand empties himself out on a walk and prefers it.
I wouldn't stop your girl from going straight out to relieve herself when she gets home as you don't want her to start going in your house.
Stop worrying about it enjoy your girl and enjoy not having to lug bags of poo round on your walk it may happen soon enough.