I've had a lot of curious thoughts about the relationship with her father and that whole storyline. Did that experience help make her a killer? Was she a bigger participant in the murders her father committed than the film makes obvious to us? Does she take things into her own hands because of her horrible experience with authorities as a child?
I think it's all about control. She lost control of her life (for a while) because of her father's murder spree -- I don't think she was a knowing part of it but the media attention, the bad treatment by police, all left her without a feeling of control. Sometimes she still feels that (the scene where she's told off in the cafe).
That is what the video game stuff is all about. As a video game exec she's in control of an entire (virtual) world and all its details; that job choice makes sense if you consider her thirst for control. Also, right after the rape, what does she do? She takes control of her environment, sweeping up the broken vase. She takes a bubble bath, as if to say, "I may have been raped, but I'M still in control of this evening."
When her father dies, that is also the start of her relaxing her control. By the end of the movie, you see her letting her ex-husband play her company's finished video game, a metaphor for the fact that she's letting him back into her life instead of holding him at arm's length (just after that she refers him to her colleague to start planning his game idea). By the way, the video game imagery is important throughout; at the end, you also see the female video game character (which was assaulted/murdered earlier in the movie, an obvious stand-in for our main character) "reborn" out of an egg/pod thing into a powerful, independent character ready to kick ass (another metaphor).