ESH. You both could've handled this situation much better than this fuckery. If you'd both communicated more during those rough 2 years, you may have even not cheated on her at all, thus preventing the whole thing. You at least should've been upfront when you realized you liked Katy. Maybe Serena would've spared you if you'd had the balls to be honest from the beginning. As for her part, it's understandable that she was upset, and the urge to get revenge os natural, but again she should've confronted you about it instead of praying to some kind of demon or demigod for said revenge. Yall both need to work on your communication skills. Although I'd guess you won't make it out of this alive to do so.