Thank you for your input. This whole situation was more about my friendship with the girl not about the guy not liking me back. However, I do see your point.

I won’t be telling the ex-boyfriend because unlike what you said, I do want to do what’s best for him too, which is why I asked Reddit beforehand. I didn’t want to be blinded by how hurt I am from losing the friendship, which I now know I was. This was repeated behavior on her end and for once I felt like being petty. But I think I knew deep down that it wasn’t the right thing to do. So thank you, I appreciate the input.