Wow, I didn't know you have been following her for all this time. Looking at your join date, I thought you had found her quite recently.
As for me, I already told how I discovered her: I knew a certain song that I really liked when I was a child, but I could barely recall its rhythm. So, one day about four years ago, I decided it was time to know what song it was. And I found it: Moi... Lolita. I could even remember some parts of the official video. But, as you can imagine, the joy of my discovery was soon replaced by a completely different emotion.
So I think the first time I saw Alizée might be in 2002/2003 because it is when she became famous here in Italy. But honestly I don't know if it is correct: my only memory of Alizée from when I was a child is ML official video, so it could be possible that I saw her for the first time years later. I don't know. I was only 5 in 2002...
Anyway, the date I could consider to be the day I discovered Alizée is 4th April 2016. It doesn't mean much, but that day I add the first Alizée song to my Spotify playlist. Back then, the only albums on Spotify were 5 and Blonde and the song is Je veux bien. So I think I might have discovered her 1-2 months before.
Edit:
Oh, and this is the video I saw four years ago: