Good friend, good lover?

This is none of my business, but it's affecting me. I can't tell why. Is it because she's my mate or just because I think what she did is near to immoral of the normal behaviour of a girlfriend. I can't stand it anymore, yet another part of me did not want to confront her about it. My friend, as old as I am, should be responsible enough for her actions, anyway what I deem as immoral might not just be to certain individuals.

My friend happily attached to a man she claimed she wants to marry is flirting with men. Well, flirting is not wrong, as long as you are single and available (by this, I mean not married). But that was much more than flirting... She was behaving too intimate with a man. And that man coincidentally is also my friend. What can I say?? I'm not going to stop two persons who have at least "some interest" in each other. Yet I can't understand how she could do this when what she assured everyone else was she was just making this man yearned for more. Made him craved!

Isn't that cruel? I'm wondering how unfair this is to her own boyfriend, at the same time to this man. It sounds really stupid, but it is upsetting me to see a good friend acting like this. A disappointment I will not want to say more. Deep inside, I actually felt so bad, because I can't imagine having a partner behaving like this - she's not my partner, okay!

I hope one day when she finds real love, she will not be this fickle-minded. For now, I just don't want this incident to be ruining my mood further, so full-stop.