she's doing this for her dad
only... I think she's being far from selfish..a person who is selfish is someone that's puts themselves before others, that only thinks about themselves and not others, but here she's done the quite opposite she put her dad and family's izzat before her own happiness. I understand she's ruined zain's life along side hers but zain is to be blamed for the mess she's in at the moment, had the marriage only broken due to dahej I don't think ghulam or usman would have been so adamant on getting aliya married so quickly, but the fact tht questions were raised abt her character has caused them to make this decision and questions were raised on her character due to Zain so he is to be blamed for the mess she's in.
also, her happiness (in her opinion) is not with zain yet she's gone ahead and married zain... recall how when she says Yes, she speaks to herself and says "apne abbu kiliye mujhe har saza manzoor hai" - this means that she considers her marriage to zain a punishment for her... not something she's happy about at all...