I'd actually like to point out that, outside from Rulue's rivalry with Arle over Satan, Rulue is actually a positive figure in the Puyo/Madou Universe. defending it from world ending disaster (Madou Sega Saturn and Puyo 7), and she's not as selfish or antagonistic as this entry makes her to be, as she has been shown to get along with among others, Ringo (Puyo 7), Oshare Bones, and Ms. Accord (Puyo 15th) and I've never seen her antagonize anyone when Satan wasn't involved. Yes, she has arguments and disagreements with other characters, but given the fact that she is the only human without magic powers in a world with monsters and sorcerers I don't think showing weakness would be a very good idea, as a matter of fact most people in Madou act like that to a degree (think Nordic or Viking culture or demons in Shin Megami Tenshi). If she didn't have the assertive personality she I doubt she be able to survive, must less thrive in the world she's in, as there is a number of characters that get triggered or offended and have no compunctions about assaulting others, such as Incubus or Zoh Daimaoh.
I like Rulue because she is the THE most human character in the Puyo/Madou world; having the widest range of personality traits and emotions than the others, who most of which are stock personalities in comparison. If she did not possess the "flaws" she does she wouldn't have accomplished as much as she did in the Madou world, humans without "flaws" usually have a greater one, apathy.