Timeline: After the Battle of Hogwarts+
The heroine Phoebe Buffay suffered from psychological trauma after the war. She traveled and used alchemy to search for the Nibelungen, the country of the dead. On the way, she had a strange encounter and traveled back to seventy years ago.
Merlin gives her the opportunity to rewrite history.
"Knowledge is food for a Ravenclaw's soul, sir."
"Please don't stop me from exploring life."
"Didn't you try everything you could to save something?"
…
"I know I was wrong, sir."
"Don't give up on me."
"Have no doubt, ladies and gentlemen, I will always be loyal to Dumbledore."
The heroine is an academic lunatic who is obsessed with alchemy and has a very low moral sense.
The main plot will be on FB, interspersed with a lot of memories of HP, and the teacher-student relationship with Dumbledore (how much depends on your imagination), a bit like the King of Kings and the French Black Rose. He and Newt will become very good friends.
Also: The heroine's name pays tribute to Friends
Purpose: To cure those whose defenses are broken due to the magical world