Not Your Regular Asthma: A Slender The Arrival Fanfiction

Young Ally doesn't think much when she sees the paper hanging in her bedroom for the first time. But pretty soon, weird things start happening. She starts seeing some kind of being in the pool while swimming with her friends. She hallucenates at school. She can't breathe at random times.
At the midst of it all, Ally figures out that this is NOT your average asthma attack.