I've started to leave my dog, for a short while at a time, to get her used to being alone but...?

the last couple of times i've left her she's chewed the door frame. Literally eaten the wood and chewed it to bits! I always leave her fresh water, toys, her bed, and a ball filled with treats to keep her occupied. How do i stop her eating her way through the woodwork? And please don't suggest crate training, it's not an option.she's 10 months old.