I still can’t figure out whether you’re excluding the Imperius.
Miss Granger would remember the Imperius. Obliviation cannot be detected by any known means, but only a Professor could have cast that spell upon a student without alarm from the Hogwarts wards
‘She was Imperiused and then Obliviated’ looks like the likeliest hypothesis right now.
Consensus # 2 is retarded, says word of God.