I'm sorry your daughter had to go through that. Sadly however I also agree that it might be wise to use this as a teachable moment, as no matter where she goes on the internet she's likely to encounter this sort of thing. It's just that being in an MMO exposes you to more people and thus many more instances where people will give into to being jerks. Please understand this isn't me condoning what happened. However it might be better to prepare your daughter for this inevitability now so she's equipped to handle it when it happens again. Because even if she stops playing FF14 it /will/ happen again on other sites and communities unless she avoids the internet entirely.

To paraphrase the Greater Internet Fuckwad Theory:

Normal Person + Internet + Anonymity + An Audience = The potential to be an asshole.

You can't control other people being horrible. You can however equip your daughter so that she can brush those people off.