The handwritten note was written a few hours after her interrogation, whilst in solitary and whilst still being denied a lawyer. My reading of it is that she had been browbeaten to the point of confusion and was terrified at making the police angry again - and was trying to explain that she couldn't be sure of anything that she said, but was terrified at making them angry again. I think at that point she almost believed the police were right and that she had been there, but just couln't remember properly - she had been broken.
I can't imagine how terrifying it would be to be interrogated in the early hours of the morning by a team of police, all shouting at you and calling you a liar and hitting you on the back of the head if you couldn't remember something properly. She was told that she would go to prison for 30-years and would never see her family again if she didn't remember. I don't know whether I would have been any stronger in the same situation.
She was given access to a translator, who failed to act independently and instead tried to convince Amanda that she was so traumatised by what happened that she had amnesia.
RS didn't drop her alibi - he was confused about the evening they were talking about and the police wouldn't allow him to look at a calendar.
We'll never be able to prove what happened though, due to the disappearance of the tapes. However, the statements were considered illegal - and an application to the ECHR has already been made regarding using these statements in the civil trial.