Another possibility could be Trick's daughter. Given the importance of Trick in the show and his family's history, his daughter getting pregnant could bring out a lot of family - related storylines. It could also involve the politics and secrets within the Fae world as they deal with the situation of a young Fae being pregnant.
One possible plot could be that a main female character in 'Lost Girl' accidentally gets pregnant. She then has to deal with the reactions of her friends and family. Some might be supportive while others could be judgmental. She also has to figure out how to balance her normal life in the 'Lost Girl' world, which is filled with supernatural elements, with the upcoming motherhood. For example, she might worry about how her pregnancy will affect her powers or her place in the supernatural community.
Aria could be a likely candidate. She's always been a bit of a risk - taker and her relationship with Ezra has had its ups and downs. A pregnancy in their relationship could add a whole new layer of complexity.
Maybe it could be a new character created specifically for the fanfic. This new girl could be from a traveling group of merchants who Naruto meets during one of his missions. Their encounter could lead to a relationship and ultimately the pregnancy.
As I mentioned before, Dee Dee could be a likely candidate. She's always getting into Dexter's business, and a pregnancy could add an interesting layer to her character. It could show a more serious and responsible side of her as she prepares to be a mother.
It could be Tobias. Since he has a unique perspective as a nothlit, his experiences could be further explored through the discovery of a lost journal. He could learn more about his own transformation and the possibilities of reversing it, which would add a lot of depth to his character arc.
Also, any friends that Renesmee has made throughout her life could be involved. They might be there to offer moral support, or there could be some who are jealous or envious of her situation, which could add some drama to the fanfic.
The potential father might be a new character introduced specifically for the fanfic. He could be a charming stranger who swept the 'gagaga girl' off her feet and then disappeared, leaving her pregnant and alone.
It could be about the challenges she faces while being pregnant. Maybe it would explore how she copes with her new condition while still having her magical duties. For example, she might have to deal with changes in her magic abilities due to the pregnancy.
The main character is likely to be the girl who is lost. She could be an ordinary girl from a small town. Maybe she has brown hair and blue eyes. She might be shy or adventurous, depending on how the story is written. Her personality would play a big role in how she deals with the situation of being lost. For instance, if she's adventurous, she might be more willing to explore and find her way out, while if she's shy, she might be more hesitant and scared at first.
As I don't know the exact 'lost girl story', I can't say for sure who the main character is. It could be an ordinary girl with a common name like Jane or Mary.