The very first word that jumps into my mind when I see this picture is flow. There seems to be so much of it present in this picture. I really quite like how the girl falls into the water and has her dress turn into a fin in a marvelous way....it looks simply wonderful, and I very much enjoy how it connects with the water again. Yet the part above the water seems to have a life of its own, it seems vivid both in shape and colour.
Interestingly the water seems much darker, seems doomy in a way, there is less contrast in colour, and you definitely get across a feeling of ...hm, maybe not fear, but of something unexpected and not necessarily positive. Which connects with your title wonderfully.
Now when I look at the image however I see that the composition is very much split into halfs, which makes it difficult for me to decide which part of it you'd like to have dominating. The actual character is in the bottom half, but the main contrast is above. Now while I undersand that this indicates that she's leaving behind something good because she 'carelessly wished', I feel like my eyes are unable to rest on the girl. So personally I feel like you could extend the image downwards a bit, and maybe even add a faint glow from a weak light underneath. That would really enhance the feeling of something waiting for her down there, the image would suddenly feel much bigger and hint at a surrounding. It would also give the figure a little more breathing room, making her feel less caged. I understand that you want to show that she made a bad decision, but maybe you could also emphasize that now something new begins.
Plus I feel like the faint light from the bottom would be a secondary lightsource, allowing for some subtle shading on the figure and her dress. I know that this is a very illustrative piece and not meant to be realistic, but I do think that a little more shading on her arms too would just give it more dimension.
The hair I was unsure about at first, thinking that when she just fell into the water you'd expect the hair to be above her head really, but I think this way it feels better, framing the head in a way and allowing for a place in the image which is not so full of movement and thus rather peaceful. And indeed she seems very much at peace with herself. I like that.... I wonder if she is aware of what she wished for at this moment, if she is accepting it or if she is still concentrating on blowing the flower, not realising what is happening with her.

Lastly, a rather technical critique... I think you should maybe re-upload a slightly less compressed version, because especailly in the dark water the artifacts from the compression are very much noticable. It distracts a bit from the image.

Nonetheless, I very much enjoy this image. I do realise that some of the things I critiqued may very well be part of what you wanted to express, so maybe it is rather a different view on it than a critique. But in any case I think that this is a wonderful and very imaginative illustration.

Daniel