One common theme is friendship. Often, the OC forms a strong bond with Rosalie. Another theme is self - discovery. The OC might be on a journey to find out who they are, and Rosalie may play a part in that.
There's a fanfiction called 'Rosalie's Redemption Arc with an OC'. In this story, the OC plays a crucial role in Rosalie's journey towards redemption. The author does a wonderful job of weaving the OC's story into the existing 'Twilight' universe. The relationship between Rosalie and the OC is complex and well - written, making it a must - read for 'Twilight' fans.
Well, for a fanfiction where an OC is heartbroken by Rosalie, you could look for ones that explore themes of unreciprocated love. Maybe the OC has deep feelings for Rosalie, but she is either oblivious or just not interested. Some fanfics might show how the OC tries to win Rosalie over but fails miserably, like in 'The Failed Courtship of OC and Rosalie'. It could also be that Rosalie is already committed to someone else, causing the OC's heartbreak as seen in 'Rosalie's Unattainable Heart'.
Well, in fanfiction, Rosalie and Emmett's daughter could have a very different personality from her parents. Maybe she's more of a peacemaker compared to Rosalie's sometimes fiery nature. She might befriend humans more easily, which could cause some tension within the vampire family as they try to keep their existence a secret. It could also lead to her having her own set of adventures, like trying to find a way to co - exist with humans without breaking the vampire laws.
A characteristic is the exploration of their emotional connection. Since they are both vampires, they have a unique bond. Fanfictions might explore how they deal with their immortality together. Some stories also focus on Rosalie's past traumas and how Emmett helps her heal. They often have a lot of romantic and passionate moments, which are a big draw for readers.
To write such a fanfiction, start with the build - up of the relationship. Let the OC and Rosalie interact in a way that the OC starts to develop feelings. Maybe they have a common interest or they save each other's lives. Once the feelings are there, have Rosalie do something that shatters the OC's hopes. It might be that she chooses someone else over the OC. Then, to really show the heartbreak, describe the OC's emotions in detail. How they cry themselves to sleep, how they can't focus on anything else anymore.
One great Rosalie Hale OC fanfiction is 'The Newcomer'. It has an interesting OC who shakes up the dynamics in the world of Rosalie. The OC has a unique backstory that ties in well with the Twilight universe.
One main theme is self - discovery. Rosalie, in these fanfictions, often tries to figure out who she is beyond her vampire nature while being domestic. Another theme is family. As she takes on a more domestic role, her relationship with the Cullen family members is explored more deeply.
One possibility could be that their daughter has special powers. In the Twilight universe, it's not unheard of. Maybe she has a unique ability to control the elements, which sets her apart from other vampires. This could lead to a whole new set of adventures and challenges for her as she tries to keep her powers a secret from the human world while also dealing with vampire politics.
The twin could create jealousy in Rosalie if Emmett shows too much interest in the new character. Since Rosalie is very protective of her relationship with Emmett, any threat, even if it's just a perceived one from her twin, could cause a rift between her and Emmett. On the other hand, it could also strengthen their bond if they work through it together.