I wouldnt be too worried about it. You said you guys were in a rough spot, and her "emotional cheating" could be what saved you the hell of her actually cheating. She just needed somebody else she could share with because she prob. didnt feel she could share with you at the time. It was 5 years ago and she openly came to you with it. I would give her a good hate fuck and then be thank her for her honesty and let it go