Oh the irony! 😂😂😂

My friend has been on this constant rant about how no one respects what a marriage means. How people get married for the wrong reasons, husbands cheating on wives, etc. SHE'S DATING A MARRIED MAN!!!! She's fully aware he's married. But she says it's okay because "he only married her for the air force benefits. They don't love each other and cheat on each other." For a YEAR I have been trying to get her to use her common sense and see WHY she should NOT be involved with this prick. He left for Germany in January to be with his wife to get the full benefits and she's been going on about how if he came back she wouldn't be with him because their relationship is wrong etc etc. Well, he came back last weekend. She's dating him AGAIN!!! What do I do? Besides drop her? I'm actually really considering this because this is ridiculous and I don't wanna hear it.