"for accessing protected computers without authorization"
The above quote appears a lot in the things she was charged for, and the basis for saying she accessed computers without authorisation is that she had violated the myspace ToS, therefore losing her permission to access/use the myspace website.
At least this is my understanding from the coverage I've read.
Quoting from other register articles on the subject:
"prosecutors charged Lori Drew with conspiracy and hacking for violating MySpace terms of service that, among other things, forbid the creation of fictitious accounts"
"The indictment charges Drew, a resident of O'Fallon, Missouri, with three counts of unauthorized access by violation of MySpace's terms of service and one count of conspiracy."
Although, if they were wrong then I appologise, since I haven't checked any other sources...