In a situation like that, find your lighting and setup and keep shooting while talking to her. Tell her something interesting or funny or just goofy. Eventually you'll capture a smile, a glimmer in an eye or something. This looks looks almost agitated that you're taking the shots. Like a half-hearted attempt at a smile. In the first one, I'd have put her left hand on her hip. That's a naturally confident pose, and it probably would've helped rotate her torso into a more flattering position -- and maybe helped her smile! 
But technically speaking, these are nice photos. Just remember that only half a portrait photographer's job is taking the photograph. 