I really like 'Elena and Rebekah: A New Alliance'. In this fanfiction, an outside threat forces them to team up. The author does a wonderful job of exploring their different strengths and how they complement each other in the face of danger.
A common plotline is them competing for the same guy, which leads to a lot of tension and interesting character development. For example, in some fanfics, they both have feelings for Damon, and this rivalry makes for a very engaging read.
Perhaps she wants Elena to understand her better. Rebekah may feel that Elena has misjudged her in the past, and by sharing her story, she can show Elena her true self.
In some fanfictions, there could be a plot where Rebekah and Elena become friends because of their shared experiences with the Salvatore brothers. They might bond over the fact that they both have complex relationships with Stefan and Damon. Rebekah could give Elena some insights into the vampire world from an original vampire's perspective, which Elena finds useful in her own journey.
Often in fanfiction, their character development is intertwined. As they interact more, they both change. Rebekah might become more empathetic due to Elena's influence, and Elena could become more street - smart in the ways of the vampire world with Rebekah's guidance. Their relationship could shift from one of animosity to one of mutual respect and friendship, which is a significant development for both characters in the Vampire Diaries fanfiction universe.
Maybe it involves her family history, like her relationship with her siblings. Rebekah might talk about the old days, their powers, and the feuds within the family.
Rebekah was significant as she was the one chosen to be Isaac's wife. Her kindness at the well was a sign that she was the right person. Her role was crucial in continuing the family line of Abraham through Isaac.
It could be Marcel. He has a long - standing relationship with the Mikaelson family, and his connection with Rebekah could deepen during her pregnancy. He might be the one to support her through the difficult times.
There could be Klaus. Since he is Rebekah's brother, he would likely be part of Bella's life in some way. He might be a protective uncle or a source of conflict if he has different ideas about how Bella should be raised. Another character could be Elijah. He might act as a mentor to Bella, teaching her about their family's history and values.