Yes, there might be some interesting ones. You can start by looking on popular fanfiction websites like Archive of Our Own or Fanfiction.net. Just search for 'bella swan is annabeth chas' and you'll likely find a variety of stories with different interpretations and plotlines.
I'm sorry, I haven't actually read 'Summer Anniversary by Chas Adlard' so I can't give you the full story. You could try looking for it in a library or searching for reviews online that might give you an idea of what it's about.
As I mentioned before, Archive of Our Own (AO3) and Fanfiction.net are great places to start. These platforms have a large collection of fanfictions on various topics, and you should be able to find what you're looking for by using the search function.
You could start by checking your local libraries. They often have a wide range of books, both popular and not - so - well - known. If they don't have it in stock, they might be able to order it for you.
One significance is that it gives Bella a different kind of support system. Instead of relying only on her regular friends, she now has a cousin who may have a different perspective on things. This can lead to Bella making different choices in the story. Moreover, it can add more depth to the world - building of the fanfiction. With Annabeth's background and her relation to Bella, new elements of the fictional world can be explored.
Well, in this fanfiction scenario, Annabeth Chas being Bella's cousin could add a whole new dynamic. Maybe Annabeth brings her own set of skills and knowledge into Bella's world. For example, if this is in a world related to some sort of supernatural or adventure setting, Annabeth's experience could help Bella out in tricky situations. It could also lead to interesting family interactions, like family secrets being shared or family feuds that need to be resolved.
Well, in a mangaer forum, you'll typically see people chatting about the latest trends in manga, debating which series are overrated or underrated, and sharing their personal collections and recommendations.