The 27-year-old actress, who has been linked to model Williams in recent weeks, said she is completely unattached, reported Contactmusic.
"I do not have a boyfriend, that can be confirmed," she said.
The 'Mean Girls' star said she cut all alcohol and drugs out of her life since leaving rehab last year.
"I don't go out with my friends and expect them not to have a drink, but that doesn't mean that I have to do the same things as they're doing.