#1 is my fav. #2 looks really odd. It looks like her face was cut and pasted onto a neck. The pose doesn't look natural.
About the skin smoothing: Leave some details....don't make the skin smoothing completely obvious. I think if people have to ask "was it photoshopped" rather than "wow she has great skin" i think you went too far.
The lighting on #1 and #3 is very pleasing to the eye. I actually love the stairwell as a backdrop. It's more interesting than most settings you're going to find around the house. Very, very pretty model, and I love her choice of outfit.
From this set, I like #3 the best - both in composition and lighting. She's a beautiful subject and you did well enough. She looks natural and relaxed. Regarding the third photo, however, I think I would have prefered slightly less empty space above her head. Well done.