I thought there was evidence to the contrary--she seemed like someone who stood up for herself and asserted herself (for example, her reaction when she found out about Henry's affair with Janice (Janice's name in real life was Linda).
You may be right about her self esteem, Vito. Who knows?
But as far as asserting herself against Henry's girlfriends, I think that was poetic license in the film. You should read "On the Run," by Greg and Gina Hill, and "The Heist," by Ernest Volkman and John Cummings. There is a ton of evidence suggesting that Henry and Karen had a VERY open marriage, including drug fueled orgies and whatnot. Henry's second wife, Kelly, actually had her own room in the same house with Henry and Karen prior to their divorce. Karen only got really upset when she thought Henry was falling in love.
