Initial thoughts/My opinion What a wonderful smile of the girl! Like her pose too, makes the image dynamic. Don't like the fishermen at the left and the large amount of space at the right though.
Content/Composition Even without the title, this image speaks of happiness: your niece looks just great and one can hear her laugh and giggle. Really greatly captured.
What could be improved here is the focal point of the image: its just the girl and everything else is un-important. The fishermen disturb, because they don't add to "happiness" but the viewer see them and so he/she wants to know what they are doing, thus he/she is taken away from the girl.
The nice river also does not add much here, mainly because the girl is not looking at it, she is just looking straight to the camera. If she would look along the river, than showing the river would have been a wise choice.
So here I would recommend a very tight crop, so tight that the branches held by the fishermen look like they are from some trees. Of course, such strong cropping only works if the image resolution permits this.
Camera work -technically The girl is a little overexposed, especially at the pink shirt and the face. Otherwise exposure looks fine. Focus is set well too, that the image is somewhat soft is more a software problem.
Digital Processing - Technical Could need some more sharpening. The border is nothing special here: I almost didn't notice it, because it's so thin.
Fits the challenge Yes, including the title it does fit very well and one of the best resolutions actually!
What a cutie! The arms or something on the top left are a little distracting, but didn't look like they could be cropped out?! I still love this - Her smile is very sweet.
She certainly does look happy - we could all resolve to be this happy at least some of the time this year. I think the light on the girl is too bright, with the hot spots on her sweater, especially in contrast to the lower key lighting on the water.
Great expression from the child. Nice colours and tone. Composition good, but wish the fisherman and branches in middle ground weren't there of course, and I might have cropped it so she were 1/3 from the left rather than 1/4. Illustrates the theme.