EDIT: What?! I'm totally Mikaze! It says so in my name right there! I've got the red hair and everything! Certainly I'm not a poorly disguised Tacticslion! I'll tell you that much right now!
So! I'm going to say Shimye-Magalla is either "chaotic neutral" (the most likely) or "neutral good" (the least likely).
The reason I'd side with "chaotic neutral" is that from what little I can find, Shimey-Magalla seems to have all the capriciousness of Gozreh and Desna combined (being effectively a goddess of storms, sea, and the like). I could, however, see a case being made for her to be neutral good as a "constant" goddess of the sea, due to her association with navigation and stars.