An interesting mod. I'm honestly not sure what to think of it, though, as Naija to me always seems so... young. That's perhaps a criticism of the game, though, and not this mod. She has the body shape of a quite young girl. I know the breasts show someone somewhat older, but that's not what I mean. The original end-body.png is best indicative of what I'm getting at. The very slight hip curvature, from the angle she's drawn at, looks more like baby fat than hips. It gives her abdomen the look of having the slight bulge of a younger girl's tummy. For how short she is, her hip curvature isn't enough to make her look older. She either needs to be taller (or more slender) with the same curve, or more curvier at this aspect ratio. Look at end-body.png and put your thumb over the top half so you don't see her breasts. It is the body shape of a girl of between 10 and 12.
You can also see what I mean if you look at the concept art. There is one shot in particular where you see three versions of Naija - two of her slightly taller, more slender, looking like a woman, and one of her shorter and looking quite child-like. It looks like it was a very conscious decision to make her look young. Naija's general look of a young girl is compounded in this mod by the lack of any body hair. Now this fact in and of itself is not bad, especially nowadays where this isn't as... fringe as it once was, and in context may even be expected in an aquatic creature. It just adds to the feel of her as being very young (and is a contrast to Li who does have hair). Additionally, in your mod the shading along the lower left of her abdomen (Naija's left) as her abdomen and left hip curve into her pubic area, is very 'deep' (continues from her hip towards her abdomen quite far) and emphasizes her abdominal 'bulge' as being child-like tummy.
All this contributes to the whole image of her being very young - unfortunately (to me) more so with this mod even than in the original game. Perhaps it's my age, and the fact I have seen my daughters go through the body stage I perceive Naija to be at. This mod, as it is, makes me slightly uncomfortable, like I'm not looking at a pretty woman, but at a naked pre-adolescent girl. Especially as a father.
My suggestion is to slim out her body a little to change her aspect ratio. Another idea that might even work better is to add some outlining in her abdomen to show the outline of some abdominal musculature - perhaps in concert with pushing the shading along her left side of her lower abdomen more towards her hip to 'flatten' out her tummy - this may give a better impression that her outer body curve is actually a lateral curve of her hips, and not a curve indicating depth. Lastly, even a slight amount of body hair might give an older impression.
Please don't take this as a criticism of the concept of this mod. I hope you will take it as constructive criticism to help make this better.
(Aside question - what is the suit that Alphasoldier has in his forum avatar?)