Is she in heat at the moment? Dogs can get very stressed out during that time, so it could explain her behaviour... but what you described sounds more like classic separation anxiety to me. And considering the lengths she takes to relieve her stress (by chewing) and the defecating in the crate, I think it's a pretty extreme one at that :/

It's going to take time and a lot of patience to curb the behaviour but it's definitely possible if you devote yourself to it