If she is that low energy, it does sound like she may be feeling ill from her allergies. What did the vet diagnose her allergies as? There is likely a less expensive way than the $100 a bag food that could help start her feeling better. When my allergies are acting up, I am miserable, hasn't happened in years, but doing anything strenuous is NOT on the agenda then.

Getting her feeling better is the best step, let us know what the vet said.

Bless you for taking her on, a husky/pit mix would be an instant "no way" for many people. You are making progress, and I bet when she is well again, with more work, you'll see progress. Given her previous existence, learning things like "play" will take time - count yourself smart to have persisted and taught her what you already have!