I watched my sister go through he same thing. A ten year relationship ending in heartbreak was devastating for her. That was three years ago, she is now bigger, better, stronger and smarter than ever so you will get through this. It says more about the other person than you. Good luck with your recovery
Cat's behaviour does not seem so bizarre to me. I think for women who are cheated on, their life after that event goes one if two ways - they close up and fight on or they go bat shit crazy. I bet the woman that Cat's husband cheated on her with is somewhat like she person she is behaving as on BB. It's like Cat is trying to fulfil this sexy, temptress, goddess type character that we can plainly see is not the real person she is. She has such a gentle, timid nature (despite the boundaries that she's continually crossing) so the vamp character she is portraying just doesn't suit her. It seems forced or contrived.
This probably makes zero sense but I guess what I am trying to say is that it seems like maybe she's becoming the woman that her husband cheated on her with? Perhaps she feels that other Cat (married Cat) is undesirable? She seems very lost to me.
Disclaimer: none of this makes their behaviour ok!