Her dose of Doxy sounds about what I'd prescribe for a dog this size.
While I realize that every vet practices differently, I typically administer anti-inflammatory drugs to my patients who have been diagnosed with tick diseases. These drugs not only seem to help with the stiff and sore muscles that these dogs have but also has anti-fever properties as well.
If she's not vomiting (which she shouldn't be doing unless she's reacting adversely to her antibiotics) and since she's not currently taking any steroids or nsaid medication, I'd suggest Aspirin at a dose of 5-10 mgs per pound of body weight twice a day. This would calculate out to be 1/2-1 of the full strength, 325 mg sized tablets twice a day. I typically suggest that this drug be given with food to avoid stomach upset althugh this may be a little tough if she's not eating.
I almost always suggest that Doxy be given with food since it's guaranteed in most patients to cause vomiting if given on an empty stomach.
You may have to force feed her if she's not voluntarily eating...which may be secondary to her fever or possibly to the Clavamox she's being given (since anorexia can be seen with this drug).
I'd mix canned food with water or pedialyte in a blender to the consistency of soup; then use a small turkey baster or syringe to dribble this mixture into the side of her mouth where there's a gap.
I have a great deal of experience with tick diseases in my patients since I live in New England where they're endemic. I typically tell owners that it often takes at least three days of Doxy before their dogs are back to normal. I've had a few cases where they responded with just one dose of Doxy but this isn't the norm. Each day should be a little better than the day before but don't expect significant improvement until after that third dose.
So, you still have another two days to go before she's back to normal...if this is a tick disease. If she's not 100% after that 3rd dose, then something else is probably going on.
I hope this helps. Deb