I can think of following possibilities..
Sanam tells ARI that she is going to leave the house coz of Nida's accusations..
or she tells him that she is agreeing for the Nikha for begum sahiba.. when Tanveer forces for the marriage
or ARI blackmails her to agree for nikha in order to repay for the money
or she apologize to ARI that she is the reason for the rift between him and Nida..and she has no feelings for him and Nida is misunderstanding
Please share your thoughts...it's fun to speculate and need something until tomorrows episode...I hate weekends ..