Let's get something out of the way first. Is this a really good movie? Well, uh, no. It's a potboiler with plenty of cliches and lots of implausible plot turns. But then, I didn't think I was getting Hitchcock when I rented it. This is a B movie, and like cheap wine and seedy beach motels, B movies have an honest job to perform. The job of a B movie, far as I'm concerned, is to hold my interest and keep me entertained without making me groan or roll my eyes too often. That's what I needed when I watched this (long day at work) and that's what I got. And I've been much more bored by (and put off by the pretensions of) movies with much higher ratings.
As for Bridget Fonda's performance, seems to me there's another way to read it. Abuse makes some people numb. Bridget Fonda's Jimmy seemed to me to be a fairly plausible depiction of a certain kind of abuse victim. Seemed to me that there were a few nice touches -- the scene in the kitchen after she's missed picking Frank up; the scene in the motel room just before the end.
No one's likely to nominate this film for any awards. But as far as I'm concerned, I got my $... worth. That doesn't always happen went I rent a movie.