Hi K.
The advice I can give is mostly from experience. I currently have 2 German Shepherd Dogs that have a high work drive. Plus, I went to school to be a veterinary technician, though not a behaviorist had a lot of contact with dogs. As somebody already said, she sounds like a bored dog. Chewing is the classic boredom reliever. The best thing that can be done for your whole family is to increase her exercise as was already suggested. It takes a big commitment to have such a high energy dog, but it is worth it as you already know. She should have a nice long ( LONG) twice a day. Play time during the day as well - fetch, chase, whatever she likes. The beef marrow bones are a good suggestion, you can get them from grocery stores and boil them for 20 minutes and let her go to town in the kitchen with it, once she has it "clean" it is safer for the rest of the house, or you can buy them very cheaply at Petsmart or Petco (already clean and some are stuffed with goodies too). Another good chewie is to take a kong toy, stuff it with peanut butter and freeze it overnight. She'll have to work longer to get the peanut butter out. Give her these types of things before you leave her. Also, someone also suggested a crate. They really are a great idea but it is sometimes difficult to get an older dog accustomed to it. I read that you rent, is it a house or apartment? If you have a yard make sure she has time outside to run around too. Some chewers are tough to break of the chewing, my youngest shepherd still goes after board books, sippy cups and plastic blocks if any are left astray while we are out.
Is she obedience trained? Does she know any tricks? If she is fairly well trained you might want to talk your husband into doing agility training with her. It keeps them both occupied!
Good luck, if all else fails, find a behaviorist who is also a veterinarian and have her evaluated for seperation anxiety. Doesn't sound like she has that, but if you can't curb the behavior after several months of the suggestions you have already received it is worth finding out before you lose hope.