How to snap Frostina using the Yo-Kai Cam?
To partially answer your question:
Yo-Kai are supposed to show what type of Yo-Kai that person would convey in the real world - how the game chooses what Yo-Kai is chosen is probably only known to the developers.
If the game has decided that the person you chose doesn't portray Frostina's personality, than a new person's photo should be used.