I know this has a bad rating, but I enjoyed the build of suspense and the fact that we got to know the characters a bit better. It was, on the whole, predictable but how many movies of this genre aren't?
If you give this one a chance and allow yourself to be drawn into the world of the characters (their arguments and issues ARE believable) you might actually find yourself enjoying it. I actually cared about Lucy's well being by the end and thing that the woman who played this part was a reasonably good actor. I found the boyfriend annoying and wondered why she didn't just dump him at one point, but I suppose that aspect of the dynamic and relationship are believable as well.
It is what it is and as an 83 minute distraction, you could do worse.