I don't have any detailed knowdge of the laws in this particuar area of the US, but it seems to boil down to a few points.
1. Is it possible to stakl someone on an internet community?
If the boy had continually tried to approach the girl physcally, perhaps near her home or where she frequents, then that would have clearly been stalking. The girl has little choice over where she lives and it is not acceptable for someone to be forced to move their home or neighbourhood because of a stalker.
But the boy is only accused of approaching her on and online community.
I regularly play an online game where certain people repeatedly attack me and even kill me. By this measure, those boys could be charged with assault, or murder!
2. The alleged different accounts which the boy is said to have opened. Is there ay evidece for these?
I sincerely hope a civil liberities group becomes involved here. If this boy is prosecuted, or worse, not prosecuted and the charge lies of file for several years, it will set a terrible precident.