It was about a brother searching for his sister who had been kidnapped to be sold as a prosttute. The brother was wearing cowboy attire and later at the end shoots a bad guy in a moving car with his rifle.

Was his sister nicknamed Alien?

Taken?

I never noticed Liam Neeson's cowboy attire. Thanks for the help!

Wait. Was that actually the movie? I was just throwing it out there because the stories kind of sounded similar.

No. I was just joking.

sarcasm can be difficult to detect when using text-based communication

I figured that but it was difficult to tell what with it being the internets and all.

There was some foreign film I saw with a plot like the OP but the girl's nickname was Alien. The movie might actually be called Alien; I can't remember.