User blog comment:FairyRaven/Fairy Tail Chapter 391: Gray vs. Silver, Review and Commentary/@comment-24066070-20140704183210/@comment-7418318-20140706141621

Maybe Keith is involved in Silviora's plans and is feeding Juvia these little bits to goad her into rushing off to come to her beloved's aid. And once she's there, Silviora can use her to hurt Gray by tormenting or killing her before his eyes.

Apart from hurting Gray, it'd also turn the 3v3 into a 3v2, tipping the favour vastly into the Demon's favour.