Actually, I'm not headed toward mystic theurge with Janis.
The only reason she has the Wizard level in the first place is because she reconfigured after the game already started and I started panicking about the prospect of getting anywhere in this game with a low hit point, low Fort save Wizard. Druid got taken mostly because it was the best way mechanically to save the real schtick of Janis, the electrical reserve feat. So she's really a sort of hodge-podge of "what can I do to make the concept work while maintaining some sense of who the character is as written." After that? Well, I've mostly just been trying to advance her in a way that kept her until the next level the best.