Where is she spending her time, money, affection, and energy?
If you try to bust the affair without evidence she will tell you it's all in your head, you are overreacting, and you just want to control her. But if you have evidence then you can be confident in delivering your message.
M22,H45,W45 S21/18D12 Retain faith that you will prevail in the end, regardless of the difficulties and at the same time confront the most brutal facts of your current reality, whatever they might be.