I have a 3 year old rough collie bitch who still chews things, she will have periods of not touching stuff, then out of the blue she starts again. At the moment she cant play down the garden as much with all the rain, she gets plenty of roadwork etc, but is just a little more hyper than the others and gets bored easily. Do you still have your other two for this one to play with? and does she have plenty of exercise. If it is wooden things or the like, you could try 'bitter bite' as mine hate the smell, let alone the taste. Problem I have is that she chews my duvet while I am asleep, yes I know I should shut her out the bedroom!! They do eventually grow out of it though.......I hope!!!!!!!