Appropriateness varies. If the abuse fanfiction is part of a story that ultimately aims to heal or show growth, it might be okay. But if it makes light of abuse or uses it in a way that makes viewers or readers uncomfortable without any redeeming qualities, it's not appropriate. Writers should be aware of the impact their work can have on the fan community.
One popular female Daryl Dixon fanfiction might be those that focus on a post - apocalyptic adventure where the female character teams up with Daryl. For example, there could be a story where they go on a hunt for a rare medicine. Another could be a story where a female survivor from a different group meets Daryl and they have to overcome differences to survive together. There are also fanfictions that explore a romantic relationship between a female character and Daryl, often set against the backdrop of the dangerous world they live in.
Daryl Dixon isn't gay in the comics. The storylines mainly revolve around his adventures and struggles in a post-apocalyptic world, not his sexual orientation.