During my treatment for Hodgkins Disease I wound up in the hospital twice for high fever, low white blood count. In my case I was told that it was just from my WBC being too low, and I was given antibiotics for a week. WBC came back up and I went home. Had a 105.9 fever once. They told me the fever or infection was just from natural things in my system that were causing me to have high fever from the low WBC.
Her's may be different.
Hope she gets better soon.