The feud between these former tweeners who seemingly had been friends for a very long time and followed nearly the same path through to adulthood has its issues in drugs.
They both love them and cause them to lash out.
Also, they are both paranoid the other is talking about them to others and selling stories to tabloids.
Selena Gomez
Demi Lovato
Source: Mr. X via http://www.crazydaysandnights.net
Read more on these