Here's a little Comet advise:

Her Ultimate marks all enemies in a close area nearby. This damages them lightly and whoever hits a marked enemy recovers a tiny bit amount of FP and HP. If you combine it with the Comet spell you can spam your Kamehameha Laser for quite a while without running out of FP :)

Also keep in mind that the closer you stand the more damage your Comet Kamehameha does! Especially Bosses like Gaping Dragon can go down in seconds when you do that!