I had a post-op infection and my WBC was not even elevated. Lucky for me (or not) mine was pituitary and I could smell it. There was no escaping it. No antibiotics helped. I did run a bit of a low grade fever for a while though and felt bad. I ended up having to have it cut out. Oh well. I felt better immediately, It sure smelled better!
Make sure she is sleeping well, eating well, and as enzy said, check out her vitamins as those will impact healing. A good multi will help as will adding D3 and making sure she is well hydrated. That is just standard for any good healing, infection or not.
She just had blood work yesterday, but I don't think it was to check for vitamin, mineral & enzyme deficiency. They are looking for infection, lyme disease and something else I can't remember. That is an excellent idea to check for the vitamins/min/enz deficiency. Her diet isn't that great either. Do you think taking over the counter supplements would help?
She could still have an infection other than in the brain, without fever, that could be causing the headaches. Surgery will cause severe deficiencies of vitamins (especially B vitamins, important for brain function), minerals, and enzymes. Has she had a metabolic panel done recently (blood test), to check for deficiencies?