Quoting lostlove: but seriously I can imagine how so many women especially those who are the caregivers can easily get wrapped up in some nice guy who pays them a little attention.
How about my W, who is not a care giver or bread winner?
As you pointed out, attention goes a long way. But the most important thing is to draw the line somewhere. You draw it far away at the door of the house; OW did not. She might have thought that inside the house was okay; being friends were okay; chatting and party-throwing were okay. They misjudged their ability to resist the chemistry that could come naturally and unnoticed. They did not draw the line far enough to prevent this tragedy from happening.
Some realize it before it happens. That is why you draw the line far enough. Some may realize soon enough that they made a mistake; not just a financial one, but also one that could wreck the family. Your H is smart enough to recognize that. Some just stray with no returns. My W is likely to be one of them.
I think this is the difference between you and many WAW.
I hope this line of thinking would help you understand where OW is coming from, and, perhaps, be more compassionate towards her for her mistakes and pain. At least I think you are.
It was a great job. Maybe the next step is to stop calling her, lostlove .