The only solution for Honour Killing is to change the idea that a girl comes under the control of the husband and therefore the caste of the husband and therefore is completely lost to the parents.
If it is proclaimed that a girl will always be independent and will in no way be controlled either by the husband or by the caste to which the husband belongs, then the parents will not be as afraid or as threatened as they are in the thought that they are losing their girl forever and therefore their self-respect forever.
If they and the entire society accepts that the girl is as much if not more on the same level as a boy, then they will not have any fear of losing their girl. The girl is only herself engaged in finding a boy and is not getting trapped in any way into a situation where she cannot ever come out of. If the girl finds out that the boy is not suitable for her, then she can at anytime walk back to her parents.
Parents must teach their children about the suitable financial conditions for a marriage, instead of just waiting for the girl to fall in love, and then to use violence against their own girl, in the fear of losing her. If the children have some basic idea of what marriage involves, it will lead to a sub-conscious hesitation.
And after their instruction to the children, if the children fall in love, then the parents must accept it, that if either the boy or the girl make a mistake, they will have the power to walk out without any problem.