She becomes more in tune with nature. As a centaur, Hermione is closer to the natural world, and this makes her more aware of the environment around her. For example, she starts to notice small changes in the forest that she might have overlooked as a human - shaped witch.
Hermione may become more cynical. The Hunter world is often dark and full of danger. Dealing with constant threats can harden her and make her view the world in a more jaded way compared to her relatively more optimistic self in the Harry Potter series.
She loses her moral compass. Normally, Hermione is a very ethical character, but in these fanfictions, she may start to see the dark arts as a viable option without hesitation. This could lead to her making choices that harm others, like casting harmful spells on those who oppose her.
One great Hermione and centaur fanfiction is 'The Centaur's Guidance'. It shows an interesting relationship between Hermione and a centaur as they explore the Forbidden Forest together. The story has a great plot that combines adventure and a touch of mystery.
As a ghost, Hermione might become more detached from the physical world. She could be less focused on grades and more on the spiritual aspects of Hogwarts. Her patience might also increase as she now has a different perspective on time.
Hermione would probably develop a much harder exterior. Bellatrix is a cruel and unforgiving figure, and Hermione would need to be tough to survive in her presence. She might become more calculating in her actions, always thinking several steps ahead. Her knowledge of magic would also take a different turn. She'd be exposed to dark magic, which would either make her more determined to fight against it or, in a more complex scenario, make her see some aspects of it that she hadn't considered before. This could lead to internal moral dilemmas that shape her character in new ways.
In 'Hermione is a Lady' fanfictions, Hermione often becomes more refined. Her speech might be more polished, and she may be more conscious of propriety. For example, she might use more formal language when interacting with others. Her actions also tend to be more elegant. Instead of just rushing into things like in the original stories, she might take a more calculated and graceful approach.
A common theme is knowledge exchange. Since Hermione is a very intelligent witch and centaurs are known for their wisdom, stories often involve them sharing knowledge, like in 'Hermione and the Centaur Sage' where the centaur teaches her about ancient magic.
One idea could be that Hermione turns into a centaur as a result of a misfired spell during a Defense Against the Dark Arts class. She could then struggle to adapt to her new form, having to deal with the physical differences like running on four legs and having a horse - like body. Meanwhile, her friends Harry and Ron would be trying to find a way to reverse the spell.
Hermione might become more protective. If her twin is in any sort of danger or facing difficulties, she would step up more. For instance, if the twin gets bullied for being different, Hermione would use her wits and knowledge to stand up for them.
She might become more sophisticated in a French way. The French are often associated with elegance and a certain refined charm. Hermione could pick up some of these traits, perhaps in her speech or mannerisms. For example, she might start using more French phrases in her conversations.