Is there a conspiracy theory about Avril Lavigne?

Thank you for asking this question; it made my day. 
This has become a pretty common conspiracy theory across certain sectors of the internet! Unfortunately, I think the only people who could know the real truth on this are Avril herself and her possible body double. 
Essentially, the theory is that when Avril Lavigne started gaining popularity for her music, she started using a body double named Melissa Vandella to help deal with all of the press/publicity because it was too much for her to handle alone (so not a clone, just an actress who looked like Avril). Then, around 2003/2004, the real Avril Lavigne died, and her record company somehow got fake Avril to take over, covering up the death so that they could keep making music and making money. A lot of people say the differences between her music from the early 2000s and her more recent music support this theory. 
Keep in mind, this is all a conspiracy theory—I'm not saying that any of this is true. 
But it could be.