Why has my 9 year old dog started chewing?

She's always been really sheepish and shy, because she was abused quite badly before we got her. I don't know too many details about it, but I don't really want to. I know she'd get burned with cigarettes and hit for basically any dog-like behavior like barking. She seems depressed and always has these sad eyes, but I'm trying to work on it (also any advice for that would be good). Anyway, she takes objects like plastic toys and takes them to the corner of the bed and chews them even when we're around. She once took a wooden stick out of the bin 3 times after I thought I'd put it in a safe place away from here. Why does she do this? I really don't want her choking but she always seems to get something even when I deliberately hide it from her, I usually find out and take it off her,but I've tried giving her chew toys and she doesn't care much for them.