Farzana Parveen died after she was set upon by more than two dozen attackers armed with bricks outside Lahore's High Court on Tuesday, including numerous relatives, for marrying against her family's wishes.
Police were present at the scene but did not stop the mob killing Parveen, who was three months pregnant.
Parveen's father Mohammad Azeem was detained at the scene of the attack. Four others, including an uncle, two of her cousins, and a driver were arrested late on Thursday.