First of all, no doubt she cheated on you but now she is married, so you can’t do anything about this. You don’t know the reason why she did the marriage but now you have to respect her decision. You can surely confront her later but not at the wedding. She really needs to give you an explanation. But try not to create a scene at her wedding and calmly talk to her somewhere else. She might be getting married due to some kind of pressure. I would suggest you, take some time to digest this matter and then try to contact her for once, as you need closure. It might get difficult for you to move on from her but you have to as you have the rest of your life and you can’t waste it on thinking about her.