One common theme could be her dealing with the pain of past mistakes. Since Sunset Shimmer has a complex backstory, fanfictions might explore how her past actions haunt her and cause her emotional hurt.
I'm not sure of specific 'Sunset Shimmer Hurt Fanfiction' titles offhand. You could try searching on fanfiction platforms like Archive of Our Own. There are likely many stories there that might fit this theme.
In 'Sunset Shimmer Abused Fanfiction', it often has a different character arc for her. Instead of the typical growth in power or friendship like in other fanfictions, here she has to deal with the trauma of abuse. This leads to a different set of challenges and development for her character. Also, the plot usually revolves around the abuse and its consequences, which is quite distinct from fanfictions that center around other aspects such as her magical abilities or school life.
One great Sunset Shimmer and Twilight Sparkle fanfiction is 'The Bond Beyond Magic'. It delves into their relationship as they face a new magical threat together. The story is really engaging as it shows how they combine their unique magical skills to overcome difficulties.
They might interact in a way where Naruto sees Sunset as someone in need of protection at first. But Sunset would quickly prove that she can hold her own. They could end up in a situation where they have to rely on each other's skills. For example, Naruto's speed and strength combined with Sunset's magic could be used to defeat a powerful enemy. They would also share their dreams and goals, Naruto about becoming Hokage and Sunset about achieving something great in her own world or in the Naruto world if she decides to stay.
One great 'human x sunset shimmer fanfiction' is 'A New Beginning'. It has an interesting plot where the human character helps Sunset Shimmer adjust to a new life in the human world. The relationship development between them is really engaging.
A common theme is redemption. Since Sunset had a bit of a dark past in the MLP universe, many fanfictions focus on her journey to make up for her wrongdoings and become a better person, or pony in some cases.
There's a fanfiction called 'The Forgotten Spell'. In this one, Sunset and Twilight discover an ancient spell that has been long forgotten. As they try to decipher it, they face many obstacles. The beauty of these fanfictions is that they can take the characters in so many different and unexpected directions, allowing fans to explore new relationships and storylines involving Sunset Shimmer and Twilight Sparkle.
The theme of identity is very common. Sunset Shimmer has to figure out her new identity as a human. Love and relationships are also themes that pop up. It could be platonic love with friends or a romantic interest in someone. And the theme of exploration is there too, as she explores the human world, its culture, and its opportunities.
One great 'Twilight x Sunset Shimmer' fanfiction is 'A New Beginning'. It beautifully explores their relationship as they face challenges together in a new magical realm. The author does an amazing job of developing their characters and the plot keeps you hooked from start to finish.