Why Would an Adult Dog Suddenly Start Chewing Furniture?

[Miss P]

The problem: Molly is a year-old rescue dog, probably labrador/border collie mix. She is spayed, and there are no other animals. She was fully crate trained, and had been eased into having the run of the house once the bladder control and teething issues were over. She still has the crate and blanket, but we don't lock the door. She'll sit in it when I'm in the room, but prefers sleeping on the floor beside the bed. She has an anxious personality - always has to be near you. Hence the floor beside the bed. We generally don't allow her in the bed, and sometimes not in the room, in which case she'll sleep right outside the door. She is eager to please, however, and was very good about knowing what was hers to chew and where she was allowed to go to the bathroom. Once we worked through the teething stages, we'd had no further chewing problems . . . until now.

After about four months, she's suddenly evicerated two couch cushions in the space of two weeks, both while we were gone, but not gone for any unusual amount of time or in an unusual time/manner. There have been no new family members, no new rules, no other behavioral changes. She will always appear anxious to some degree, but not more so than normal. We haven't gotten lax with the amount of appropriate chew toys around, she has a mountain of bones. One side note: when she was a puppy, we initially gave her some puppy stuffed animals to chew as well as puppy chews, but had to stop that because they wouldn't last more than five minutes before being destroyed. She hasn't had a stuffed animal since about last February.

My ideas:
I'm going to restart the crate for a bit, and am thinking about getting some bad-tasting spray if I can find some that won't stain (it's a white couch). We're on the lookout for any chewing so we can immediately re-direct. I thought about supplementing the bones with stuffed animals, she really seems to like shredding, but thought it might exacerbate the problem because she'd get the idea that soft cushy things are acceptable to chew. Another idea - get a second animal for companionship while we're gone, possibly a cat.

Besides any other hints for resolving the symptoms, I'm really looking for ideas as to the cause - why would she spontaneously start this up? I feel like something has to be the trigger, since she's usually so eager to please and smart about what's hers and what isn't. I wonder if there's some reason that she feels anxious or upset enough that the emotional satisfaction of chewing outweighs everything in her mind.

Anyone else have this issue?