You posted the link to the wikipedia article, if you had actually read it it says EXACTLY who made the last remarks, who made the account, who initiated it etc. Read/post etc.
the last message sent by the Evans account read
Does not say who said it specifically.
later admitted creating the MySpace account with her daughter and Ashley Grills, Lori Drew's 18 year old employee
So three possible people could have said it.
The only thing the article said definitely was the mom initiating the contact to find out what Megan said about her daughter.