cute images, however, watch your focus and get your flash off your camera; it will provide your more interesting looking frames. These look a bit soft, however not a bad first attempt. Is not this a sweet 15? not 16?
Pretty girl. If you had bounced the flash off of the wall to your right that would have provided a nice portrait light.
The same pattern would have strengthened the second image too by throwing the broad side of her face into a soft shadow.
The third shot is nice of her but the strong flash darkening the background is not a good look. If the surrounds are not visually great you can still often find a plain wall which would be a better backdrop. Again bounce from another side wall. Usually the wall opposite the broad side of her face.
If she had a particularly thin face then you would reverse that lighting advice and bounce off the wall on the same side and the broad side of her face.
The shadow of her nose on her cheek in #1 looks like you had the camera in portrait orientation with the flash on the left. If you're using the built in flash and don't have the option to bounce, turning the flash to the right side on that shot would eliminate that.
