Your sister is still in her reproductive age and quite young. I am unsure about her familial status, whether she has completed her family or not.
But considering her age, I would advise surgical excision of the lesion along with electrocauterization. This is the best option given her age, and will also help in maintaining her fertility
status, in case she decides/wishes to have a child in the future.
Please discuss the same with your doctor or surgeon. Hope this helps.