I interepret the story as her wanting to marry the prince, thus Jacob's aquiscence. The initial act was likely concenting. However, ultimately, it was Jacob that failed to watch over his daughter and permitted the circumstance to happen. The defilement accusation is my interepretation of the brothers' actions, not mine. There likely was also a percieved fundamental incompatibility between the groups, and offer to intermarry was only part of the ruse on the part of the brothers.