User blog comment:FairyRaven/Why did the Celestial Spirits invite Lucy's group to the spirit world?/@comment-904888-20120724064034/@comment-4829046-20120724130212

I see you didn't read his comment too well. "Still, Hiro could make it so that someone like Gajeel or Mira or Elfman or Cana could go with them. Why Levy?"

What Raven means is that Mashima probably purposely put Levi into the fray because she will be important while as the other FT members will not be that important in comparison.