Hi there... her surgery sounds a lot like it's oral tongue not base of tongue, especially based on treatment. If so it's likely not HPV related though one never knows - stranger things have happened.

Treatment sucks BIG TIME, more so than the surgery. The surgery is nothing - really I was on a beach two and a half weeks post op. I looked like I'd been hit by a truck but there was little pain. The problem with a neck dissection (bilateral) is that you will have some weakness in your shoulders and arms and numbness and tightness in your neck, jaw and ear - for a bit. It never truly goes away but it does improve - I had physio and did the exercises while I was walking my dog. You should recover fairly quickly from the surgery - then radiation slaps you back down ;o(

You will get there though... stay strong.