One important thing is to do research. Learn about the real - life impacts of an abusive childhood. Then, when writing about Emma Swan, focus on her emotions and how she might struggle but also show her strength. For example, you could write about her nightmares and how she tries to overcome them.
When writing this type of fanfiction, be very careful with the language you use. Avoid using offensive or triggering terms casually. Try to show the story from Emma's perspective, how she felt during the abuse and how it shaped her view of the world. Incorporate elements of hope and resilience. Maybe she finds a hobby or a passion that helps her cope. And always be prepared to listen to feedback from readers, as they may have personal experiences related to the topic and can offer valuable insights on how to make the story more sensitive.