Donny,
Why do you want everyone to know this?
What purpose does it serve?
All this maliciousness on your part is childish and so unnecessary. It shows further poor judgement on your part abd a huge defect in your character, tbh.
Regardless of the facts how YOU see them. It should have never been brought here or the "threat of exposure" should have never been made by you. This is not high school. This is life. It's was none of our business.
BTW, since you've now made this everyone's business - if you've been broken up for some time now and you know she's continued fucking Spannow, why does it matter that she's doign it on your birthday?
If you guys were supposed to be "friends now" why shouldn't she?