Jack picked up the rock she'd intended to use and nodded slightly. She was taking all this on some guy's word, but for now, it would have to do. She'd had a crazy life so far, though seeing as it was all she knew, it was fairly normal. She'd seen things most people didn't, and she'd grown to believe things quickly. She wouldn't call this Cas person a crazy quite yet.
"He's here on the island?" She started swinging the sling, not looking for any target. She'd have to work on targeting a little later. She just wanted to make sure the vines didn't break with the force. The sling made the appropriate whir, and soon she let it go, or one side anyway. The rock flew, not straight up but in a speedy arc.
"Will have to work on that. These vines bite though." She picked up the other sling to test it. "Hate to rip up a shirt already, but it might work best for a finger wrap." She shrugged absently and loaded the second sling.