So one of my female readers helped clarify the I saw him first rule that I described the other day.
According to her, the whole female loyalty thing only affects whether a woman is going to make the first move or not. When the right guy makes the first move, all sisterhood is out the window.
This make perfect sense to me, and it also explains several of the exceptions to the rule that I've seen over the years.
Now I have to ask MixedSignalGirl why she didn't fill me in about this nuance of the rule.