Im very worried for her, shes in denial

Maybe as a joke, you can say........."You bhabi and devar hang out with each other so much that people could easily mistake YOU BOTH for being married. It wouldn't be fair to your older brother, lol" And then laugh.

^You can either do that.............or mention the issue in a general fashion with your bhabi. Just say........."I care about you as my cousin. I know you're a good wife who is faithful to her husband. And you have a good relationship with your dewar....but it's good to maintain a little distance because of the conservative culture we live in." (If you say it like this.......you're not making any accusations.)

After this..................BACK OFF! Don't push the issue further because you can risk putting ideas in their head. Not only that..........you can get in trouble as well. What if your cousins tell their parents about your comments........and then your aunt/uncle accuse YOU of having a dirty mind? Know what I mean?

So, pick one of the above ideas (either make a jokeful warning....or talk to your female cousin about it).............but only say something one more time........and then don't discuss the issue again. They are adults and can decide how to conduct themselves.

It's not affecting YOUR life or marriage.........so don't get too involved in it.