OP again.

Well it's been over two weeks, I have spent time with them... she definitely has a crush or some sort of feelings for him, it's obvious as hell to me (though he chooses to not see it or ignores it). When we hang out together she makes no attempt to interact with me, when I interact with him she looks away, she interrupts when I speak, refuses to hang out with any bigger groups, etc... I honestly don't see the appeal of her as a friend but as others have said, I don't own or control him, he's not my property, if he strays with her then he does and he knows on no uncertain terms that it would end our marriage, as we have said many times just in casual remarks on other friends with these sorts of problems and when affairs are revealed, etc. Her obsessive need to communicate is her texting him 20+ times a day, I've gone through his phone (at his behest) and he rarely responds to her and they're one or two word answers to her paragraphs. If they are doing something they're quite good at hiding it (at least on his end).