Why did Colin Farrell hook up with that psycho chick?

I think that interlude, like much (or all) of the movie, was symbolic of an aspect of romance in real life. Specifically, I think it represented how so many people in real life -- to avoid loneliness -- attempt to pair up with someone who is not really a good match.

He was getting desperate as his time to meet someone was running low. So he focused on the minor positive characteristics he liked about her (her short hair and accent) and tried to pretend he wasn't bothered by the major negative characteristic he really didn't like (her heartlessness). But in the end, the major negative proved too important and the relationship did not last.

Well it does seem a poor choice to make at first glance and that his stay was almost up definitely came across as a reason. However if we take this poor choice and stack it with the many poor choices this character makes i.e. blatantly being too friendly with his true love in the apartment which he should know would anger the new leader he is with but he is so dumb and always making poor choices that he carries on anyway. If we take these decisions and stack it with the choice he makes at movies close...... what a dumb son of ... . Plus who would choose a lobster. All in all a perfect in character choice for that character. To close yes a poor choice for you and I and a perfect choice for that lobster brained character. This is backed by no fact other than what I took from this movie.