Dev is able to stick to his decision becoz he is getting for d reason came to bose house i.e soha's love and trust.sona was there for dev.when he himself asked her leave what could she do.even asked again If he really want ,while leaving see looked towards ishwari wid hope.bt none stopped her.
I would suggest u to read dlavanya di "GET OUT -Then and Now "post. Ur confusion and doubt ll b clear i hope.