I think in my opinion, because both sisters are tied to KV, by banding together, they can cure CS. It’s just they haven’t tried. Honestly, they dont really know the extent of their powers yet. Drishti, Shivji ki pratna kare aur speed se shaktiya mile the. I think with Ra’s powers of healing and DriDiv channeling their energy to Ra, he can save his father without the KV. Akhir KV’s shaktiya, vo dono ki under henna ? So shouldn’t they need to channel their powers together to save CS.