13-year-old girls don't talk that way
"So now I'm Marty. Just Marty. A girl named Marty. It is the bane of my existence."
Yeah, no.
The writer must have been very proud of this bit. If only he/she'd found an appropriate character for it. To have this come out of the mouth of a 13-yr old is to insult the intelligence of pretty much anyone over 13.
I would have appreciated the story more if Marty had turned out to be a construct of Willy's imagination. If the brother had said, "Nobody's moved in next door that I know of." This would have meshed with the fact that Marty has no parents and seems to just show up on the scene at every opportune moment. Yeah, it would have been a little hokey, but at least it would have worked.
Either way, she's not real. And I say this having liked the movie.
Note: Marty's even less real than Portman's Mathilda in The Professional. Mathilda, while equally precocious, was credible because she'd gone through severe trauma at a young age which caused her to take on certain adult characteristics. At the same time, she was revealed to be still a child in significant ways. Marty is straight up Tinker Bell.
That's the most you'll ever get out of me Wordman. Ever. -Eddie Wilson