The guild as a whole would be in mourning. They would hold a big memorial for her. Her death could also inspire some of the younger members to train harder so that they can prevent such tragedies in the future. For instance, Wendy might focus more on her healing magic, hoping to be able to save lives in similar situations in the future.
Gray might become more brooding and withdrawn. He would blame himself if he was involved in any way that led to her death. Her death could also be a turning point for Erza. She would become more protective of the remaining members and might even change some of the guild's rules to better protect everyone in the future.
When Lucy dies in a fanfiction, it might cause a rift among the guild members. Some may blame themselves for not being able to protect her. Her death could also be the start of a new adventure as the characters search for a way to resurrect her. This could lead them to explore new magical realms or encounter new enemies. Plus, it could change the power balance in the guild as her celestial magic was quite unique and important.
One possible scenario could be that she sacrifices herself to save her friends from a powerful dark magic. In the chaos of a huge battle, she might use all her magic power to create a shield that protects everyone else but drains her life force completely.
In many fanfictions, Future Lucy starts off as a determined and somewhat broken character. She has seen the destruction of her world and is desperate to change it. As the story progresses, she learns to trust the people in the past. For example, she might initially be hesitant to work with Natsu and the others, but as she sees their kindness and determination, she becomes more open. This helps her character grow from a lone wolf trying to save the world to someone who is part of a team.
Some writers justify Lucy's death by making it a noble sacrifice. For example, she might give up her life to close a portal that would otherwise release a great evil upon the world. This way, her death is seen as necessary for the greater good of the entire Fairy Tail universe, including all the kingdoms and innocent people in it.
Happy, Natsu's companion, would also be very sad. He was used to Lucy being around and would miss her presence. The whole Fairy Tail guild would be in mourning. Erza, for instance, would feel a great sense of loss as Lucy was like a little sister to her. This could lead to changes in the guild's dynamics, with some members becoming more withdrawn while others might try to be stronger to honor Lucy's memory.
It can completely change the mood. If Gajeel dies, it brings a sense of gloom to the usually upbeat Fairy Tail world. The guild members would be in mourning, and their actions would be centered around avenging his death or dealing with the loss. For example, Pantherlily might go on a quest for justice.
It can also have a big impact on the characters. For those who have been directly affected by Acnologia's actions, like the dragon slayers who have a special connection to dragons and thus to Acnologia, his death can be a very emotional moment. They might struggle with mixed feelings of relief and guilt. Relief that the threat is over, but guilt because they may feel they could have done more or differently. This internal conflict can be explored in the fanfiction and add depth to their characters.
If Lucy never joined Fairy Tail, the friendships and relationships among the characters would form in a very different way. Also, many of the story arcs might not unfold as they do in the original plot.
In some fanfictions, Lucy might be portrayed as a friend to Frosch. She could be someone who looks out for the little Exceed, given her kind - hearted nature in the Fairy Tail series.
One possible fanfiction could be that Lucy is invited to a grand ball in the magical world. As she enters the ballroom, a mysterious melody starts playing. Lucy, being the confident and graceful character she is, starts to dance. Her celestial spirits watch in awe as she twirls around, her dress flowing with each movement. It could be a dance that not only showcases her beauty but also her connection to the magic within her, as she uses a bit of her magic to create a sparkling effect around her while she dances.