One popular storyline could be about two female Animorphs who develop a deep emotional bond during their battles and shape - shifting adventures, which then turns into a romantic relationship. Their unique abilities as Animorphs could add an interesting dynamic to their relationship, like how they might use their powers to protect each other in different animal forms.
There might be storylines where a female Animorph falls in love with another female character who is not originally part of the Animorphs group. This could create a lot of conflict and drama as they try to navigate their relationship in the context of the ongoing war against the Yeerks. The differences in their worlds and loyalties could be explored in depth.
Some storylines may focus on the coming - out process of a lesbian Animorph within the group. How the other Animorphs react, whether they are accepting or face some challenges in understanding. It could also show how this relationship affects the group dynamics as a whole, and how they all continue to fight against the Yeerks while dealing with this new aspect of their teammate's life.