Read other letters about this article
The Qur'an enjoins "modesty" for Muslim women so that they can be distinguished from non-Muslim women (who, in the Medina of Muhammad's time, would have probably been slaves, and thus subject to the sexual whims of their masters, and the master's friends).
"Modesty" has been interpreted in a variety of ways by scholars and Muslim communities. There has always been a confusion between clothing as a "sign", which can be perfectly arbitrary (a sash that says, "I'm a chaste Muslim woman" on an otherwise naked female) and clothing as a way to hide any manifestation of a woman's physical presence, which the scholars and community *hoped* would prevent sexual signaling and sexual disorder. That strategy fails because humans (male or female) always find a way to present a sexual self even in the most self-abnegating clothing. Put a woman in a burqa and she can flirt with her shoes, her walk, her nail polish. Put a girl in a school uniform and she'll roll up her sleeves, hike the skirt, and experiment with makeup. If you try to extinguish the signalling with ever more restrictive rules, people will find a way around the rules.
That said -- the commentators focussing on the issue of hijab are missing the point. The hijab, for that Pakistani, symbolized a commitment to behaving as a proper, modest Pakistani Muslim female in all contexts, inside the home or out of it. Not only did Aqsa reject the hijab, she LEFT THE FAMILY HOME. That, I think, was something that her family felt it could not ignore. If she was sleeping outside the home, she was possibly, even probably, engaging in sex. The family's honor was being destroyed and the men were being humiliated in front of their peers. The obsession with hijab on the part of the Western media is distorting our understanding of what were "probably" the reasons for this honor killing.
I say "probably" because we know so little of the Parvez family history, the family dynamics, that we may be missing some crucial facts that would explain the father's actions as something other than generic honor killing.