My guess is that she'll try to use her leg a good bit while she's young, but as she grows taller, and the distance between the end of her leg and the ground gets greater, she will use that leg less and less.  I find that to be true with Edward.  We do have another Shiba in our meetup group who lost a leg when she was hit by a car.  It was a back leg at the same point at your pup's.  She does use the leg somewhat for getting up and laying down, but they just make sure to have rugs around for her to lay on and a soft bed.  She doesn't have any problems from using the leg.  My best advise is just to try to touch and handle the stump as much as possible while the pup's young so that it doesn't become a problem later.  Same thing you'd do for a puppy's feet to get them used to it so cutting nails is easier.  It will help desensitize the stump.  I tell my human patients the same thing about their legs.