* It's never explicitly stated in the books: J.K. Rowling never provides a clear, direct answer to what specifically happened to Ariana Dumbledore.
* The events are shrouded in mystery: What's known is primarily from vague references by Albus Dumbledore and the general assumption that it was a violent encounter with Muggles.
Here's what we know from the books:
* A group of Muggle boys attacked Ariana: This happened when Ariana was a young girl. She was caught in the middle of an altercation between her brother, Aberforth, and the boys.
* Ariana suffered a mental breakdown: The attack traumatized her, and she was never able to fully recover. This resulted in uncontrollable magic and dangerous spells.
* The incident led to the tragic death of Ariana: She died many years later, presumably as a result of her mental illness and the strain of controlling her magic.
What we don't know:
* The specifics of the attack: The extent of the violence and the nature of the Muggles' intentions are unknown.
* The long-term impact on Ariana's mental state: It's unclear how much the attack directly contributed to her mental illness or how much was due to other factors.
Important Note: While the events are portrayed as a Muggle attack, it's important to remember that the books do not condone blaming all Muggles for this tragedy.
Conclusion: It's difficult to state definitively what the Muggles *did* to Ariana Dumbledore. We only have a limited understanding of the event, and its impact on her life was profound and tragic.