I'm not sure of a specific 'bella helps a mopy paul twilight fanfiction' off the top of my head. But you can try searching on popular fanfiction websites like Fanfiction.net or Archive of Our Own. They have a vast collection of Twilight fanfictions and you might find one with that plot there.
Maybe Paul is having trouble controlling his werewolf side and Bella, with her knowledge of the supernatural world, tries to help him. For example, she could use her connection to the Cullens to find a way to soothe Paul's inner turmoil.
The plot could potentially start with Bella stumbling upon Paul in a rather downcast state. Paul might be mopey due to his unrequited love for someone, or perhaps his conflict with the vampires in the area. Bella, being the kind - hearted person she is, decides to step in. She could start by simply listening to Paul's problems, which is something not many in the Twilight world might do for him as he's a werewolf. As she listens, she realizes the root of his mopey behavior. Then, she uses her knowledge of the Twilight world, her relationships with both vampires and werewolves, to help Paul. Maybe she arranges a meeting between Paul and some of the more friendly vampires to ease the tension, or she gives Paul advice on how to win the heart of the person he loves. Through her actions, Paul slowly starts to come out of his mopey state and become a more positive character in the fanfiction.
Well, Twilight fanfiction is quite diverse. In general, if you're looking for a story where Bella helps a mopey Paul, it might involve Bella using her empathetic nature. Maybe she tries to understand Paul's problems, like his struggle with being a werewolf in the Twilight universe. However, without actually finding the specific fanfiction, it's hard to say exactly what would happen in it. But it could be a really interesting take on the characters and their relationships.
Another theme is the transformation of Paul's character. Often, in these fanfictions, he starts out as a rather rough or wild character, but through his relationship with Bella, he becomes more gentle and understanding. For example, in some stories, he learns to control his temper better. The third common theme is the idea of a different kind of pack dynamic. With Bella being involved with Paul, it changes the way the pack views her and also how they interact with Paul. It can create some interesting power struggles and alliances within the pack.
It's also about the chemistry that can be created between the two characters. Paul is a werewolf with his own set of traits, and Bella is a complex human - turned - vampire. Their interactions can be full of tension, both in a good and bad way. For example, their different views on the vampire - werewolf feud can create interesting conflicts and resolutions in fanfiction.
One popular one might be those that explore an alternate universe where Bella and Paul form an unexpected alliance against a new threat in Forks. It could be interesting to see how their different personalities interact outside of the typical Bella - Edward - Jacob triangle.
One popular 'twilight paul and bella fanfiction' is 'Paul's Redemption'. It shows an interesting take on how Paul and Bella's relationship could develop outside of the main Twilight narrative. It delves deep into Paul's character, exploring his more tender side towards Bella.
One common theme is the struggle between different supernatural worlds. Since Paul is a werewolf and Bella is involved with vampires, there's often a theme of conflict and coexistence.
One challenge could be the acceptance from the two different communities, the werewolves and the vampires. Another might be the safety of Bella during the pregnancy, as it could attract unwanted attention. And of course, there's the relationship between Paul and Bella, which may face strain due to the sudden change in their situation.