Sylph did like trees a lot, to her they were sacred as the offspring of the world tree Yggdrasil. Cain thought that her seeing the forced being defiled by Morena's breath, seeing him at death door, the pain from the forced summoning, how the plans at the elvish kingdom could fail, and how long she will need to get back. Cain could easily imagine her going into a rage and going on a dragon-killing spree.
Alice quickly teleported toward Cain with Sofia to heal his wounds, Cain's wounds were more severe than anyone else so she had to let Sofia wait.
As he was blacking out, he could feel familiar magic by his side other than Alice's magic, it wasn't that of Sylph, it felt similar to Sofia's in some way. Sofia was unconscious and probably out of MP so it couldn't be her Hot and crispy, like a sensation chili pepper.
