Assuming the data at the end is for all the shots, you are using too wide of a lens. The ideal focal length is around 80-100mm, as it is a flattering level of "compression." 14mm is way too wide for a portrait shoot of this style. Lighting wise, your best bet is to have your sister be farther away from the background, and light the background a few stops lower, so your subject is a few stops brighter, and then use a wider aperture (say around f3.5 or f4). That way, you will have separation in not only lighting, but in the focal plane.
Goodluck and hope my 2 cents helped!
Regards,
Jake