Well, perhaps she jumps in the pool without her glasses because she's in a rush to join her friends. Once in the water, she realizes she can't see clearly but still has a great time playing water games. Later, she might worry about how she'll find her glasses when she gets out.
Maybe it's a tomboyish girl who doesn't care about losing her glasses in the pool. She's more interested in having fun and being active in the water.
There could be a heroic rescue. Maybe her friends or family notice she's missing quickly. They start looking for her and manage to track down the kidnappers. Since she doesn't have her glasses, she has to rely on her other senses like hearing to help her stay alive until she's rescued.
She could end up in the wrong part of town. Maybe she was supposed to be at a library but ended up near a noisy construction site because she couldn't read the street signs clearly without her glasses.
Perhaps the girl without glasses is near the pool, and someone accidentally bumps into her, causing her to be dunked. This event might be a turning point in the fanfiction. It could lead to her meeting someone new at the pool, like a boy who helps her out and they start a new friendship or something more romantic as the story unfolds.
In the fanfiction, the girl without glasses could remember the layout of the house in great detail. Even though she can't see well, her memory serves her. She starts to crawl on the floor to avoid the smoke and uses her memory of the rooms and hallways to make her way towards the exit. Along the way, she might find other survivors and help them as well.
The main character would obviously be the girl without glasses. There could also be the person who dunks her, whether it's a friend, a rival, or just an accidental bystander. Another possible main character could be someone who witnesses the event and then becomes involved in the girl's story afterwards, like a lifeguard who has to deal with the situation.
She might struggle to find her way out of the pool safely. Without her glasses, her vision is blurry and she could accidentally swim into the pool's edge or other objects.
Maybe she's in a new, unfamiliar building and without her glasses, she's trying to find the exit. As she feels the wall, she discovers a series of marks or carvings that are part of an ancient mystery related to the building. This discovery could then lead her on an adventure to solve the mystery and learn about the history of the place.
She could use her memory of the environment before she lost her glasses to her advantage. For example, if she knew there was a particular landmark near the place she was kidnapped from, she could try to move in that direction once she escaped the immediate area where she was held.
She might be in real trouble without her glasses. Since she is often the brains of the group, not being able to see clearly could make it hard for her to find a way to escape. Maybe she tries to use her other senses like hearing to figure out where she is.