A possible scenario is that Ginny is chosen to represent Hogwarts in an important inter - school event. She then has to practice with students from other schools, and one of them seems to be getting a bit too close to her for Harry's liking. Harry starts to feel jealous as he sees Ginny having a great time with this new acquaintance and wonders if she might like this person more than him.
In some fanfictions, Ginny might start spending a lot of time with a group of friends that Harry doesn't really like. She seems to have more fun with them, laughing and joking around, and Harry feels jealous because he wants to be the one she has the most fun with. Also, Ginny could receive a lot of fan mail from admirers after she does something heroic on the Quidditch pitch, and Harry can't help but feel a bit jealous seeing all the attention she's getting.
One common scenario could be Ginny flirting with another boy in front of Harry. For example, she might dance with a popular Quidditch player at a Hogwarts party while Harry watches. Another could be Ginny getting a lot of attention from an older student for her academic achievements, and Harry starts to feel left out and jealous. Maybe Ginny is also asked to be a partner for a special project by someone other than Harry, and she seems really excited about it, which makes Harry green with envy.
One possible scenario is that Harry masters a new and powerful form of magic that Voldemort has been unable to attain. For instance, if Harry discovers a way to combine different branches of magic in a unique way that gives him an edge in battles. Voldemort, who has always been obsessed with power and being the most powerful wizard, would surely be jealous of Harry's newfound abilities.
The theme of envy is also very prominent. Dudley envies Harry's connection with Ginny, which is often portrayed as deep and loving. He may also envy the magical world that Harry and Ginny are part of, which adds another layer to his jealousy. Another common aspect is Dudley's struggle to come to terms with his own feelings, as he's not used to feeling so envious.
One common theme is unrequited love. Harry might be in love with Ginny but unable to admit it, so he feels jealous when she's with Dean. Another theme could be self - discovery. Through his jealousy, Harry realizes his true feelings for Ginny.
A third scenario could be jealousy. If other witches start showing interest in Harry and he doesn't immediately and firmly shut it down, Ginny might get mad. She is a proud witch and doesn't want to share Harry's affections, and his seeming indecisiveness in such situations could lead to her anger in fanfiction.
One plot could be that Harry is partnered with a new female student in a project at Hogwarts. He spends a lot of time with her, studying in the library and discussing magical theories. Ginny sees them together often and starts to feel jealous. Harry might not even realize at first how his actions are affecting Ginny.
She might act overly friendly with other guys. For instance, she could be really touchy - feely with them, like hugging them a bit too long or playfully hitting their arms. This would make Harry jealous as he wants her attention all to himself.
One scenario could be that Ginny has prepared a special surprise for Harry in the common room. She has decorated it with floating candles and their favorite flowers. When Harry enters, she plays a soft, romantic song on her wand - charmed radio. They then slow - dance under the candlelight, lost in their own world.
Well, a major theme is the struggle with emotions. Harry is used to being in control, but when it comes to his jealousy towards Ginny, he's all over the place. Also, the theme of growth is there. Through dealing with his jealousy, Harry grows as a person and becomes more understanding in his relationship. Plus, there's often the theme of the power of love, where in the end, love overcomes his jealousy.
In this type of fanfiction, Ginny's jealousy could stem from a few factors. First, Ginny has always been protective of Harry. If she senses that Draco, who has a history of being a bit of a bully and on the opposite side in the past, is getting involved with Harry, she might be jealous. It could also be that she's jealous of the new dynamic between Harry and Draco. Maybe they are solving mysteries together or having adventures without her. Ginny is a strong - willed character, and seeing Harry share things with Draco that she feels she should be part of could easily make her jealous.
One scenario could be that Harry is overly protective of Ginny after the war. While it may seem like a good thing, Ginny is a strong - willed witch. If Harry starts treating her like she's fragile and tries to limit her activities, she would get angry. For example, if he doesn't let her participate in certain dangerous but important magical tasks because he's afraid she'll get hurt. Also, if there are rumors or false accusations about Harry in the post - war wizarding world, and he doesn't share them with Ginny right away, she might be mad that he didn't trust her enough to confide in her.