My wife just admitted she cheated.?

I understand your feelings about this but if you wanted to separate from her before this happened then you need to do what is right for you. Don't be horrible to her about this yes she did something terrible to you but be the bigger person. End the relationship if you feel you need to and leave it at that. Don't drag it out and be a jerk just end it and go your separate ways. Even though you do have a child together you can still raise your child without being together. Just make sure your child is a priority.