My dog tears up my bedding when I am gone. Do you have any ideas?

I have a 9 month old Doberman. I am training her to run the house while I am away. She gets on the bed and chews the blankets. She does not touch anything else in the house and she knows it is bad. She truly does nothing else wrong, no trash, furniture, shoes, nothing. My last dobe did the same thing with our bedding for almost a year and a half before finally quitting. They sleep on the bed, so they are not jealous. She gets a treat every time she is good. Do you have any ideas. Thanks