Heav'n has no Rage, like Love to Hatred turn'd,
Nor Hell a Fury, like a Woman scorn'd.
-- William Congreve
There's an ugly part inside of me that wants your love for nobody but myself.
-- Belldandy from Ah! My Goddess: The Movie
Belldandy is almost always unfailingly polite and kind, but in spite of her status as a goddess, this doesn't mean she is without vices. The love she shows for Keiichi can be one of her most endearing qualities, but at times it can also lead to jealousy which is downright terrifying. When she suspects that someone is trying to steal Keiichi's affection, or that Keiichi is perhaps paying too much attention to another woman, Belldandy sometimes unconsciously releases her powers resulting in sudden paranormal activity. Since she is not in control of these outbursts, the effects are random and sometimes destructive.
What makes Belldandy's reactions somewhat confusing is that she sometimes becomes jealous over someone's mere proximity to Keiichi, while other times she seems oblivious. For example, when Skuld ages into a young adult and begins to develop feelings for Keiichi, Urd warns Belldandy that Skuld has fallen head over heels for him. Belldandy calmly replies that both she and Skuld love Keiichi very much, causing Urd to comment that it just goes to show how stable their relationship is.
While in the manga the first signs of Belldandy's jealousy came with the amateur exorcist Shiho got a bit too close to Keiichi, it is shown much earlier in the anime TV series. When Marller decided to use Senbei, the Demon God of Poverty and Misfortune on Keiichi, it led to a number of incidents where Keiichi appeared to be hitting on another woman. He fell on Sayoko, lifted Megumi's shirt (it should be stressed that he was possessed by Senbei), and barged in on Sora as she was changing. Each time there were overt signs of Belldandy's jealousy, ranging from a powerful electrical storm with purple lightning, a sudden torrential downpour of rain, and a force that bent pipes, barrels, and lockers in the Auto Club's clubhouse. Belldandy seemed unaware that she was the cause of these phenomenon, but as soon as she realized Keiichi wasn't to blame things immediately returned to normal.