Use of an acid solution to burn off something is what is done for genital warts which are caused by HPV, not HSV. Herpes and genital warts present differently, so I'm not sure what this doctor is talking about unless your fiancee has both warts AND the Herpes OB and the doc is talking about removing a wart in this fashion.
If you all had typical Herpes OBs with sores or blisters that are healing up with the antiviral meds, and she has no other bumps/warts/lumps-looking things down there, I say she just cancels the appointment, or be prepared to go in there and hold her ground while having a conversation to understand what the heck the doc is talking about.
We have an HPV folder here, so if you all believe she does have warts, that may be a good place to start doing some reading for the basics.
Yep, I wouldn't be letting anyone near my hoo-hoo with acid unless I saw genital warts and understood the treatment options. I also *think* that they can biopsy something that is suspicious and I might insist on that first. Then if it did come back positive for HPV, the acid treatment might make sense.
C.