It's also about respect. I learnt that i never showed her the respect that i thought i was, she also never showed me respect either.
The only reason someone will actually cheat on you is because they have lost respect for you and themselves. Without respect, there is no love. Show her the respect that you think she deserves, as your W. But that means saying no to her and putting yourself first too, until she can show respect to you and your family.
Just cos things are going right, doesn't mean that they were always wrong.