She bid her time and enacted the vengeance she deemed appropriate.

Not appropriate, but necessary to get out of the sittuation.

The reason why you should not and cannot do that under the law is that you weren't defending yourself anymore, you were literally taking vengeance or revenge at that point.

Some women in this sittuation retaliate when the man is asleep. The other in a direct reaction to the humiliation. In this case, it is defense.

You can't look at every case through paragraphs. It is important to take into consideration psychology of the people. Being beaten regularly for five years with apologizes coming right after or without them, both changes the way people think to a great extent. Law should not be translated to favor abusers over their victims.

There is no justified murder.

I disagree. Past records a lot of murders pardoned by the independent courts.