Perhaps she'll run into a super powerful villain that doesn't exist in her own dimension. This villain could pose a great threat to her and force her to use her wits and skills in new ways.
She could meet an alternate version of herself. This other Amy Rose might have different values or goals.
She might run into a group of rebels. If the alternate dimension has some sort of oppressive regime, there are likely to be rebels fighting against it. Amy could get involved with their cause and help them in their struggle.
Well, she might encounter different versions of her friends. Maybe a Sonic who has a completely different personality or abilities. For example, he could be a dark Sonic in that alternate dimension.
She might encounter strange creatures. For example, in many alternate dimension stories, there are unique beings that don't exist in our world. Maybe she'll meet a talking animal or a floating jelly - like entity.
Even one of her friends like Tails could be the betrayer in a really unexpected plot twist. Maybe Tails is forced to betray her by some external threat. For example, if an enemy captures Tails and threatens to harm him or Sonic if he doesn't give away some important information about Amy Rose or lead her into a trap.
There could be a wise old wizard - like figure in the other dimension who guides Amy. He has lived for centuries and knows all the secrets of this strange place.
A 'amy rose dies fanfic' could be a very sad and dark take on the character. It might explore themes like loss, grief among the other characters who knew Amy Rose. Maybe it's a way for the writer to show how her death could impact the whole story's universe.
Well, the 'angel of darkness' is likely to be a main character. It might be an entity with its own motives and powers. Another character could be Sonic. He might play a role in trying to save Amy Rose from the influence of the 'angel of darkness' or be involved in some way in the events that unfold.
Another possible main character could be her rival. This rival could be from a different boxing school or have a completely different boxing style. Their interactions both in and out of the ring would be a major part of the story.
To write an engaging Amy Rose birthday fanfic, think about the setting. It could be in the Sonic universe, like in Station Square or Angel Island. Describe the place in detail. For the plot, you could have a mystery where Amy's birthday presents go missing. Her friends suspect a new villain, but in the end, it turns out to be a misunderstanding. This creates drama and keeps the readers interested.
One idea could be a story where all of Amy Rose's friends plan a surprise party for her. They decorate the entire Green Hill Zone with her favorite flowers and prepare a huge cake in the shape of her Piko Piko Hammer.