It's been discussed many times. Back when she had her first album Psych and she had a concert in Moscow, I came out with a very critical post of her which I referred as the Stalingrad post. I warned of trouble if changes weren't made. Some were made, but not meaningful changes; not changes that would make a significant difference and that's what she needed. Four albums later and she's still making the same mistakes.
As far as the split, Alizée's a very private person and never really discussed it but I believe she did she say they parted on good terms.
But one of the rumors going around back then was that when Jeremy came into the picture, he her told for one, she should have been making much more money and also that many of the songs she was singing had a much deeper sexual meaning than Alizee was aware of.
Now Mylene apparently uses sex to sell. She even designed her own sex toy and wrote a song about it and Mylene's sexy reputation was no secret to Alizee or her family. I believe MF/LB got to okay from Alizee's parents to let her read the book 'Lolita'. So they knew up front, sex, and sexiness was going to be a part of what she was doing. But some people feel the Freudian terms of some of her songs went deeper than the obvious sexiness.
I'll give you a couple of examples of lines from J'en ai marre that were supposedly written in Freudian terms;
Des extrêmistes à deux balles,
Extremists with 2 bullets. How many extremists only have 2 bullets?
Je brule à l'ombre des bombes
I live in the shadow of bombs
What kind of bombs? Is she talking about a war between countries, or something again, of a Freudian nature?
These 2 lines, though I think are Freudian in nature, seem nothing earth shattering, but it shows there was more to these lyrics than meets the eyes and I'm not going any further than this here. You might want to read some of Homer's interpretations in this forum of the different songs.
So like I said, allegedly Jeremy told her of 'deeper' meanings of those lyrics that were already sexy and rumor and I stress rumor is it bothered her and was the other reason she left.
Another 'rumor' I heard is the reason she waited until 2007 to put out another album was she was still under contract with MF/LB to do another album and the only way to get out of it was to wait for it to run out in 3 years. Of course she had the baby not long after leaving which is probably the best reason for the delay until 2007.
While we are on this story line, I might as well take it a little further. It is again rumored that one of the songs on this first album was about Mylene Farmer. The name of the song is Idealizer. There were plenty of interpretations out there and looking at these and looking at the lyrics, I wasn't happy with them. I didn't think they did a good job at all. Now I want to point out I know little French. I just had 2 years in high school so many years ago. That has helped me in following Alizee and I've picked up some more in these 10 years. Still, when the show SAGA came out and Chritophe Willem sang 'Idealizer', I wanted to make a separate video as I did for many segments of the show and I wanted to add 'accurate' subtitles, so I spent a lot of time finding the meanings of those lyrics and if you listen to those lyrics, you can see how many people thought at the time that Mylene must've been offended by them. Keep in mind too, that in some of those lines where a male pronoun was used such as he or him,I feel they were really talking about a woman; "he (she) is no longer there", and to him (her) asked.......one last kiss". I felt putting them in would make it too obvious and then I didn't want to do that.
The song writer came out and said it was written about a trouble woman he knew, but to many, I guess those lyrics hit to close in a certain direction.
Alizee sent the first cd from the album to MF/LB and I believe they never replied.
I think they are on good terms though. Idealizer was not written by Alizee and if it was written about Mylene, I strongly doubt if Alizee knew it.