Laura McDonald posted a 4 1/2-minute video of herself impersonating Stewart Saturday, the New York Daily News reported.
As of Tuesday afternoon, it had gotten more than 700,000 hits.
"Hi Rob, it's me, KStew," she says in the video. "I want to explain what I did. You know, the whole having sex with my director thingy. I'm putting this video on YouTube because I want just you to see it."