In the manga

Silphy is another one of the sweepers that forms the Sweeper Alliance. Her specialty is body combat. She battles Deek Slasky, but he manages to deliver an attack that continually freezes her until she turns into a complete ice statue. However, while the ice is still spreading through her arm, Sven appears and fights Deek, damaging so that his Chi is not strong enough to maintain the spell, saving Siplhy.

In the anime

The same, except she does not battle Deek, as he doesn't appear, and she is attacked by Preta instead, who Sven fights to save Silphy.

Source: Wikipedia