Thanks Zahid and Baygham for your comments. I think you drifted towards general impact and missed my actual question; how to propose marriage to her family. It is appropriate for my family to approach her parents, or should they accompany some Pushtun elders as well. Or what you think is the best way.
Pakhtuns are normal human beings and have not transferred from Mars. Approach her family through your elders/parents in respectful way. Your parents should tell her parents they want their daughter's hand as they want her to be their daughter, don't ever mention that she is in love with you or likewise, otherwise you'll provoke them.
My advise for the girl would be like she should/must stand with her parents. Remember! a marriage without parents blessings is without 'barkat'.