I tend to assume she would because she speaks with one in the comics.
It's been stated on a number of occasions that she doesn't have one (though, of course, given all the writers involved over the years, there are undoubtedly some counterexamples).
A Russian master-spy wouldn't speak English with a Russian accent.
I liked the movie; it didn't have the same freshness as the first one, admittedly.
I think the limited interaction between Tony and the actual villains probably played a part in that; his meeting with Vanko in Monaco was excellent, but they really don't have any substantial scenes together after that. Sam Rockwell's Justin Hammer is well-played, but he's a complete buffoon, not really meant to be taken seriously - I thought this version of Hammer was interesting. Usually "mirror" characters are people who are like the protagonist, but better; here we've got a guy who has clearly consciously tried to be Tony Stark, but can't quite pull it off.