There are several possible reasons. Maybe she has lost something precious in the fanfiction. It could be a magical item that was important for her connection to the sea. Or perhaps she has had a fight with a friend or someone she loves. This emotional distress makes her break down in tears as she tries to deal with the situation.
In one fanfiction scenario, Ariel could be crying when she realizes that the prince she loves is about to marry another woman. She has sacrificed so much to be with him, leaving her home and giving up her voice. Now, seeing him with someone else, her heart breaks and the tears flow freely.
Perhaps in the fanfiction, Ariel and Eric get married and have to deal with the cultural differences between the underwater world and the human world. For example, Ariel has to learn the proper etiquette in Eric's kingdom while Eric tries to understand the unique traditions of Ariel's mermaid family.
In a fanfiction scenario, Ariel takes her shoes off when she reaches the shore. As she does so, she feels a strange connection to the land. It's as if the act of removing her shoes makes her more attuned to the human world. She starts to learn about different types of shoes that humans wear and even tries to make her own, using materials from the ocean. This leads to some humorous and heartwarming interactions with local villagers.
Perhaps in a fanfiction, Ariel and Eric will have a family of their own. They will raise their children to understand both the land and the sea, creating a unique bond between the two worlds.
One possible fanfiction could be that Ariel and Eric discover a hidden underwater kingdom that was lost long ago. They embark on a journey to learn about its history and find that it holds the key to a magical power that can save both the underwater and land worlds from a new threat.
Often, in fanfiction, Ursula can still be a main antagonist. She might come back with a new plan to break up Ariel and Eric, maybe using a different form of magic or disguise this time.
One possible fanfiction could be that Ariel, in her exploration of the human world, finds that being barefoot gives her a closer connection to the earth. She feels the warmth of the sand on the beach, the coolness of the stone paths in the village. As she walks barefoot, she discovers new sensations and it becomes a symbol of her freedom and newfound identity among humans.
Another idea is to write a fanfiction where Ariel has to deal with a new threat to the ocean. It could be an evil sea witch who is more powerful than Ursula. Ariel would have to use her wits and the help of her friends to save the ocean and all its inhabitants.
Perhaps in some fanfiction, Ariel's death could be due to the pollution of the ocean. As she is a mermaid, her home is the sea. If there is excessive pollution, it could make the sea uninhabitable for her and the other sea creatures. She might succumb to the poisoned waters while trying to find a solution to save her home.