Not that I really care about this story, because it is really, really weird, but just my two cents from having read some reports on the story:
1) The relationship with the fictional girlfriend started in 2009, correct? To me, that immediately disqualifies the idea that Teo did this for publicity - there is just simply no way I can fathom someone coming up with that elaborate of a plan in order to execute it 3 years later for publicity points. Teo was legitimately thinking about leaving for the NFL last year. Concocting this scheme for Heisman Trophy points (when he is a defensive player and there is zero guarantee you will even be in the discussion) makes no sense.
2) I listened to some talk radio floating out the idea that this was an elaborate cover up to disguise Teo's sexuality. More believable, but why does it involve another person who could very easily be tracked down through various internet connections? Most athletes who are gay just shut up and keep living a lie. Teo decides its in his best interest to perpetuate a fiction of a girlfried for years and then kill her off very publicly as the best way to hide this? So odd.
3) The Deadspin article makes it clear that the other guy Tuiasosopo indeed created Teo's fake girlfriend and used her to "hoax" other people. This seems to indicate that the guy probably tricked Teo too. It is not that crazy to believe Teo got pulled into some fake online relationship with another Hawaiian/Samoan girl at a good school like Stanford. This does in fact happen to people all the time.
4) However, it seems like Teo did not do enough to let the public know that he never met the girl (if indeed he is not part of the hoax.) That to me indicates at least he was either very embarrassed to admit he had an online girlfriend or that he knew she did not exist and either was a part of the hoax or just incredibly stupid in believing that the truth would not come out.
Either way, the guy's draft status is gonna take a huge hit, "guilty" or not.