Here's an exert from the USA Today article about Oliva Munn's recent movie's and talks about her time on the set of Iron Man 2 and looks like she has already filmed her scenes:
Munn has some other career highlights ahead of her. She has a part in the upcoming films Iron Man 2 and Date Night with Tina Fey and Steve Carell. "All my scenes (in Iron Man 2) are with Robert Downey and one other actor. I don't know how much I can say," she says. "We were (improvising) nd it came to me (to say a line)
(Later) Robert said, 'Can we just stop a second and give Olivia a round of applause. She is rocking it. That made me feel good."
Doesn't sound to me that she's playing a booty call which is great, still leaning to Rumiko after this article, but need to wait and see.