The body is well-rendered in both form, proportion, and color choices. The abrupt ending of the left leg, though, is disconcerting because the right leg smoothly transforms into a fish-scaled form.
The head is properly proportioned, but the hair lacks detail so it appears plastic compared to the detail in the beta fish tail. Perhaps consider giving it the same amount of detail as the tail. Obscuring the face with just some brush strokes is as disconcerting as how the right leg was ended - another place where additional detail would vastly improve the composition.