Most Helpful Girl
Well, I'm pretty sure the guy in the movie had it figured out that the girl wasn't who she said she was long before they went to meet her. They looked into a bunch of the stuff she had said and found out that it wasn't true (i.e. the songs that the girl was supposedly singing were from youtube, the studio space was still up for sale, etc.).
Realistically, you're probably not going to meet someone that crazy and with that elaborate of a story, however, there are people who might lie about certain aspects of themselves or their lives. At the very least, however, you can ask someone to go on webcam for you (most people have webcams) so you can see that they aren't significantly older than they say they are or an entirely different person. Also pay attention for any inconsistencies in the things that they tell you.