My grandmother passed away nine years ago, but before she did I'd spend a lot of time keeping her company. She was aware of present events but couldn't understand her current situation, and I was (I think and hoped) able to help her feel calm and safe by being there as someone she knew and trusted. My point though is that while she couldn't remember that day's lunch, she could still tell the same stories from her childhood that she had told me 30+ years earlier with all the detail I remember from back then.
My experience with memories and such, being around twice the average age here, is that you won't forget the things that were important to you. You'll also remember trivial things. Sometimes you'll wonder why they seemed so important at the time, or why you couldn't see what you should have at the time. But that's how life works, you hopefully learn from the past and move on. New things and situations arise that have to be dealt with and enjoyed. Life goes on.
I don't think that Alizée will be completely forgotten by any fan. I'm sure the internet as we know it will be gone as well, but I think music survives and her songs will somehow still be available. But there will be so much more created in 50/60 years
that older things would be much more difficult to discover for the first time.
And as usual I'm losing track of my thoughts so I'll just stop here.