these could all use a much tighter crop on them to really isolate the subject(s). Your niece really is pretty, gorgeous eyes, and those brown sugar freckles are amazing! I'd love to see you do a close up of her where she isn't smiling and there is some nice light in her eyes to really make the color of them stand out. I say "not smiling" because they appear to have a beautiful shape to them as well, and smiling changes the shape. That is not to say that a subject shouldn't smile, not all ALL!!! Just for the sake of variety.
I don't know how new you are to post processing, but can you see how the two color pics are very green/yellow in the skin tones? That is an easy fix and if you were to crop and print these, you should color correct as well.
My fav is the last one. If that were mine, I'd definitely crop it, taking as much of her knees out as possible and probably some of the top of her head as well. Just to really zero in on her interaction with the puppy. the white of her knees are a visual distraction, as the viewer's eyes are always drawn to the brightest part of an image, and the knees (in their entirety) don't need to be there so prominently. All that grass behind her serves no purpose either, I'd do a very tight crop on that shot and call it a keeper! Nice shots of a very cute kid and dog.