Well, one must look at the words and the implied meaning behind it.
If one takes the nuptial night as meaning actually consummating the relationship, then sure, Tunveer's threat is kind of weird.
But all she said was that Mr.Khan would spend the Nuptial night with her.
This is easily possible.
Even if Mr. Khan and Ms. Farouqui get married, Tunveer is capable of creating a ruckus - fire, fainting, stab wounds, gun shot, etc. - such that Mr. Khan is then compelled to spend the night with her...albeit in a care-giver capacity, whether in a hospital or at home!
So relax... this 'challenge' scene will most likely take place since CVs are master-writers of saas-buhoo shows and such scenes are typical fare.
This will be one more incident where Tunveer will come out ahead.
But...make note, this will supposedly happen after the wedding, so revelation of her truth won't be to far behind.
Jayne