Where on earth did you get the idea that HPV causes lichen sclerosis? As far as I know, they don't know what causes LS (autoimmune? result of injury?). It's not an infection, and I've never read that HPV was in any way involved.
Besides, your gf doesn't even have HPV. I think it stands to reason that if she had cleared the virus, then she would have cleared any related symptoms.
Lichen sclerosis has nothing to do with HPV. Clearly you and your partner have no current HPV problem. Your partner should follow her provider's advice about the lichen sclerosis; or if uncertain about his/her expertise, she might ask for referral to a dermatologist.
Good luck-- HHH, MD