1. Frankly speaking, I don't know anything about kanya dosha, sarpa dosha and vish kanya dosha.
2. I have not yet got my kundli made. My parents also don't have a belief in Astrology.
3. I would advise you to take the kundli of the concerned girl, meet a top-level Astrologer of your city, take his/her advice, purchase stone rings or some other remedial measures and everything will be alright in due course of time.
4. But you have to find a good Astrologer who knows the subject very well.
Beware! I question everything and everybody.