The B17S is basically shorter in length than the regular B17 If I remember correctly, the seat part is the same width.
I didnt find the two styles to be much different in terms of pressure on the 'girl parts', but I found the B17S to be annoying in that the shorter rails underneath didn't allow me to push the saddle back as far as I wanted to get feeling centered on my bike, weight wise.
I started with the B17S, then switched to the longer B17 which i could set back better. Then my hips were just too wide for it and I switched to the B68, which is perfect for me.
I'd suggest if she has narrow hips to get a regular (men's) B17. The nose is not any weird thing as to cause 'girl pressure'- it was no problem for me at all even on 60 mile rides.