She could be amused. Fanfiction can be really funny sometimes, especially when it takes the characters in unexpected directions.
Ada might be very curious. She'll probably start reading some of the fanfictions to see what all the fuss is about. As she reads, she could either get really into it, loving how fans have added new layers to the Soukoku story, or she might quickly lose interest if it doesn't match her taste.
There are several ways Ada could react. Firstly, if she has a creative side herself, she may be impressed by the creativity of the fans who write Soukoku fanfiction. She could find it inspiring and might even be motivated to create her own fan - related content. On the other hand, if she's a more conservative person when it comes to the original story, she may be skeptical at first. But as she reads more, she may gradually change her mind and start to appreciate the different interpretations that fanfiction offers. It really all depends on her own personal inclinations and her relationship with the original Soukoku story.
She might be really surprised. Fanfiction can be quite different from the original story, and if Ada is used to the official Soukoku storyline, seeing all the creative and sometimes wild interpretations in fanfiction could be a shock.
He'd probably be annoyed. Snape is a serious wizard and he might think fanfiction is a silly Muggle - influenced concept.
He might be curious. Harry is always eager to learn new things. He'd probably read it with great interest to figure out what this new world of RWBY is all about.
Marinette could first be very confused as to why Adrien would think that. Then she would likely be angry. After all, she is actually fighting against Hawkmoth as Ladybug. She would probably start gathering evidence to prove her innocence, like showing Adrien her normal life activities that are completely opposite to what Hawkmoth stands for.
He'd probably be shocked. I mean, Dudley has always seen Harry as the odd one out in the family, and suddenly finding out he's famous in a whole different world of fanfiction would be quite a surprise.
Jon Snow might see it as a chance to finally make the North truly independent. He would probably use the gold to fortify the Wall and protect the realm from the threats beyond. Sansa, on the other hand, could use it to improve the living conditions of the people in the North, building more shelters and providing food during the harsh winters.
Claire's reaction could be a mix of fear and determination. She would be afraid because she's in a vulnerable position, but she would also be determined to not let Ada succeed in whatever her plan is. She might start by trying to talk sense into Ada, appealing to her better nature if there is one. If that doesn't work, she would look for any weaknesses in Ada's plan or in their current location to make her escape and also try to find a way to stop Ada from doing this to others in the future.
Snape might be initially shocked but then try to hide his concern. He's a complex character. He could act indifferent in public but secretly start to gather information about who is behind the abuse. He might also start to keep a closer eye on Harry without the boy realizing it.
He might be a mix of flattered and bewildered. Flattered because people care enough to write about him, but bewildered by some of the wild ideas in the fanfiction.
Well, in many such fanfictions, Harry might be shocked at first. He probably feels a sense of pity for Draco too. After all, being under the Imperius Curse means Draco has no control over his actions.