Agreed that the story development which brings us Dana the Terrorist is rather hokey, but if I had to guess, I would say that her personal involvement with getting rid of the ex was all about making Cole more sympathetic to her and also making him her accomplice in the murder.
After being a die hard 24 fan for the last 8 years, this turn in the storyline is SO BAD, I may call it quits and say fuck it (even though, I agree, Dana is so f'n HOT, she's worth watching just for her).
Just makes no sense at all. The writers clearly hit a wall and didn't know what else to do, so they fell for the whole "inside job"/"mole" storyline angle, and didn't think it through at all. (that's what happens when different writers do different episodes). There's no way she, or the terrorists could have anticipated the actions of Kevin and his drunken loser friend, in the "van down by the river" scene, and could've easily been killed when Kevin's friend left the van to go after them and shoot them. Totally fake/bogus storyline... I expect much more from 24 writers than that garbage.