It could be a new character entirely. Maybe a hybrid of some sort, half - vampire and half - werewolf, which would be a very unique and interesting choice for her true mate. This would bring a whole new set of dynamics to the story as Bella has only been involved with either vampires or werewolves before.
The full story of 'her returned mate' might involve a series of events. Maybe they had a falling - out before the mate left, and during the time apart, both of them had time to reflect. When the mate returns, there could be a mix of emotions - joy, hesitation, and even a bit of fear. There could be challenges to overcome, like rebuilding trust and getting used to each other again. It could also be a story set in a particular time or place, which would add more details to the narrative.
I'm sorry, I haven't read 'her returned mate full novel' so I can't say for sure what it's about. But usually, novels with a title like this might be about a relationship where a mate has come back into someone's life.
After the woman returned from her honeymoon, she found that the dowry room had become her brother-in-law's wedding room. Her mother-in-law even said arrogantly," Call the police if you have the guts. Anyway, you're married. My son also has a share of this house!" The woman felt very angry and helpless. In the end, she chose to end the marriage.
It could be a werewolf. In the Twilight universe, werewolves and vampires often have a complex relationship with humans. A werewolf might have been Bella's real mate, perhaps one that she met briefly before Edward entered the picture. Maybe this werewolf had a special connection with Bella that was disrupted when Edward came along.
Love and connection are common themes. Since it's about Bella finding her mate, there's always a strong focus on the deep emotional bond that forms between her and her mate.
In the fanfiction, the sister's vampire mate might introduce Sookie to a whole new side of the vampire culture that she was previously unaware of. This could include secret vampire ceremonies or ancient vampire lore that Sookie starts to explore, all because of her sister's relationship.
She could start by looking at her existing social circle. Maybe there's someone she knows who has an interesting story or personality that would be a great addition to her novel.