To develop her character, explore her relationships outside of Morgan. Maybe she has a best friend who has a completely different lifestyle, and this contrast can show different aspects of her personality. Also, her reaction to the dangerous world that Morgan is a part of can be a big part of her character development. Is she scared? Or does she want to be more involved? Her career choice can also play a role. If she is a social worker, it can show her compassionate side and her desire to help people, which could lead to her having different views on crime and punishment compared to the BAU team.
Her character can be developed by giving her a unique backstory. For example, if she grew up in a tough neighborhood, it could have made her strong - willed and street - smart. This would influence how she interacts with Morgan and the BAU team. She could also have a hobby or passion, like painting, which shows her creative side and gives her an outlet for her emotions. Another way is to give her some flaws, like being overly impulsive or having a bit of a temper. This makes her more relatable and adds depth to her character.
One way to develop her character is through her family dynamics. If there are family secrets or unresolved issues from their past, it can shape who she is. For instance, if there was a family member who was wrongly accused of a crime in the past, it could make her more interested in justice and fairness. Additionally, her experiences in love can be a factor. If she has been in a bad relationship, it might make her more cautious or cynical, and this would be evident in how she interacts with the male characters in the fanfiction. Her character can also grow over time as she faces challenges and learns from her mistakes, like learning to trust the BAU team more as she sees the good they do.