It Doesn't Make Sense

Before you start thinking I have woman issues please note that my earlier post about the female mind was a passing comment about common perception. But since it was the only post so far that has had feedback I have put a little more thought into the topic.
Today at work I listened to my cubicle neighbour have several heated phone discussions with her boyfriend and at one point his mother. By "listened" I mean "tried to not listen". When I realized it was going to drag on for a while I put on some headphones and played the first album I could find on my harddrive. She explained that he was an unreasonable and abusive person and had made unkind remarks about her mother. Had she said the same about his mother she is sure he would have hit her.
After taking the headphones off sometime later she let me know that he had apologized for his remarks and everything was ok now. I was a little concerned for her but I know her enough to know she can look after herself.
It got me thinking though. Why do some women make apologies for their abusive and unworthy partners while others constantly complain about their relatively healthy relationships? Obviously it is not a black and white issue but sometimes it seems to me that women are more likely to deride an honorable man and vindicate a bastard.