Actually, she did both of those things. And, incidentally, it’s the false memories bit that would be impossible in Methods—Hermione, of course, did not spend years to give her parents what are apparently years worth of memories.
It’s only perfect, undetectable Memory Charms that require that much time. Giving someone years of memories in the quality that is customary for years-old memories, when no Wizard has anything against it, is probably not that difficult.
Hermione didn’t erase her own existence, but implanted false memories to get her parents to go to Australia. Distance did what magic couldn’t.
Actually, she did both of those things. And, incidentally, it’s the false memories bit that would be impossible in Methods—Hermione, of course, did not spend years to give her parents what are apparently years worth of memories.
It’s only perfect, undetectable Memory Charms that require that much time. Giving someone years of memories in the quality that is customary for years-old memories, when no Wizard has anything against it, is probably not that difficult.