The term "chasing butterflies" refers to trying to get things you really can't catch. It alludes to some people's goals never coming to fruition, as they have to be altered for the sake of goals that have a higher chance of success. It's believed that the term came from Norah Jones's song Butterflies, released in her 2003 album "Stay With Me."
Rod Bingaman's comedy of the same name (2009) seems to capitalize on this usage. After Nina Davis flees her big wedding day, her stepmother acts as a proxy to legalize the marriage. Soon, she and Nina's groom set out to look for Nina and convince her to reconsider, only to stumble upon a whole set of complications involving escaped convicts, a sex addict, and a dejected deacon.
Yet, are butterflies really hard to catch, as the idiom implies? Butterflies fly in irregular patterns, widely believed to evade predators with ease. However, some scientists say their bright colours neutralize their advantage in agility. As it turns out, their erratic flight path does help evade predators, and the bright colours dispirit predators from giving chase if they fail the first time.
Of course, assuming the predators are birds. They may not be so lucky with a mammal on two legs wielding a net. So does this imply that the groom and stepmother in the movie get their girl back? You'll just have to watch Chasing Butterflies in websites that allow you to watch movies online for free to find out.