I had a chapter with a pretty similar situation deal with this last semester. Now I know that NPC rules are different than fraternity ones, but basically, the chapter had to provide a really good reason as to why this rushee was not a good addition to their sorority. For instance, bad grades is a good reason. Being a "dork" is not. Being a legacy does carry some clout in the Greek Life world.
In any case, the woman ended up cutting our chapter after the second round, so they didn't end up with a bad situation, but alums can be really tough. Especially if they are nationally recognized and donate money. Those are the alums who can cause the most problems.
I'd give the kid a chance. And if he's a dork, he might add a little diversity
