I don't know for sure. To figure out if Millie is a real story, we'd need to know more about the plot, the source, and any background information available.
In a fanfic, Moxxie's accent could be a central part of a romantic storyline. Suppose there's a character who is initially put off by her accent but then gradually falls in love with her as they get to know her better. Her accent becomes something endearing and special, and they have cute exchanges where he tries to imitate her accent playfully.
The main characters are Striker and Moxxie. Striker might be seen as the more dominant and aggressive one. He has his own goals and ways of doing things in Hell. Moxxie, who is associated with I.M.P., has his own set of friends and a life that gets intertwined with Striker's in the fanfic, creating a lot of interesting interactions and storylines.
It can be depicted through her dialogue. For example, using specific words or phrases that are characteristic of her accent. Like she might say 'ain't' instead of 'isn't' or use some unique local slang.
You can start by looking on popular fanfic websites like Archive of Our Own (AO3). It has a large collection of fanfics from various fandoms, and you're likely to find quite a few 'Moxxie x Striker' ones there.
One popular 'Moxxie x Striker' fanfic is 'The Unlikely Bond'. It delves into a scenario where they are forced to work together on a mission and gradually develop an understanding of each other.
One possible interesting plot could be Striker and Moxxie being forced to work together on a dangerous mission. They start off hating each other but gradually come to respect one another's skills as they face various challenges.
Sorry, I don't have enough information to tell the full story of Millie drama. It could be a local or independent production that I'm not familiar with.
As of now, there's no clear evidence that Millie Bobby Brown is working on a novel. She is mainly known for her acting career in shows like 'Stranger Things'. However, she might be interested in writing a novel in the future, but we don't have any official announcements about it.