Nobody's memory is precise - and the same event will always be described differently by different people - and will usually change every time they tell the story as we are all extremely susceptible to suggestion from others and often exaggerate are own part to make ourselves appear more important. Trying to determine guilt in this way shows a total lack of understanding about how memory works.
I've spoken about this a few times, but I regularly take medical histories and I'm always amazed at the huge variations between the stories of all involved - and how much the story will evolve over time. It was always hugely embarrassing when a patient tells you something that he later denies and claims to have no recollection of mentioning when he is reviewed by the Consultant
Also great post above Bill - the language difference is going to have a huge impact. Raffaele was translating for Amanda and this is always going to lead to inaccuracies and misconceptions - this has nothing to do with guilt
I do find it interesting how people seem so obsessed with the minutiae of everything they said or did, but have no interest in the glaringly obvious indicators of their innocence.
Nearly all 20-year olds are a bit chaotic and often don't handle situations in the most mature way. If I came home to find my house door open now I would be very concerned, but thinking back to student days, I probably would have acted in a similar way to Amanda as you are so used to people coming and going in the house. At university, I remember a group of four boys having their house burgled whilst they were all home. One of them left the door open and am opportunist walked in and stole their TV etc. - they didn't notice anything as were all in their rooms - I'd loved to have seen them explain that to the Italian police