Luna sent Hermione the information her father had on the locking spells. As much as the Ravenclaw had suffered from bullying under Dumbledore's watch, she thought Hermione had suffered more. She wanted her friend to her answers, even if could be in danger once Dumbledore was free from his portrait. He might inform the Order about her involvement. And she still had a year of school left with vengeful types like Ginny Weasley. It would be best for her if no one knew of her new allegiance. Hermione was determined to keep Luna's involvement from him.