User blog comment:FairyRaven/Fairy Tail Chapter 391: Gray vs. Silver, Review and Commentary/@comment-24066070-20140704183210/@comment-7418318-20140706143541

"If that was his plan, it was only necessary to say Gray is in danger"

No it wouldn't. That Silver just took Gray and is fighting him one-on-one now is enough to know that Gray is in danger. And since she didn't immediately run off to look for him it's apparent that just knowing that Gray is in danger is not enough to make her abandon the others.

But if she learns that Gray isn't just fighting the physical battle, but also has to fight against his own emotions because Silviora is both Gray's nemesis and occupying the body of Gray's dead father, it might be enough to push her over the edge and make her go after Gray.

Maybe the chances of this plan succeeding are low, but the risks are even lower. Fairy Tail won't be able to use the information Keith told them to their advantage anyway, so it's worth a try.