I have had GBS since Sept. 29, 2012, (1 yr + 4 mo); it affected both legs up to my waist. I was very fortunate that it stopped where it did (though I often forget to feel fortunate). I now walk with a cane, but my balance and control is terrible. In answer to your question regarding headaches, dizziness, and nausea: I have never had them in connection with my GBS.
I am not sure of the dizzyness and stuff. My mom suffered from GBS and has recovered fine other than some neuropathy in her legs and feet. It is wonderful that your daughter is recovering.