A mutual divorce has been filled by my sister-in-lawfor which she has demanded 5 lakhs.We have alreday paid her 2.5 lakh.But for the rest 2.5 lakh a post dated cheque was issued with a condition that when divorce will be done she will encash it.But the divorce was not done on the said date and we had done a stop payment.Now is is telling that she will file NI act 138.How valid is this law in our case.Please help us.