So you told her you condoned her being interested in Don and she told you after the fact that some making out happened. When was it that this "FYI" was supposed to occur? Like, they're on the street, they look into each others eyes, they start slowly moving in for the kiss, the wind is blowing gently, sensual blues can be heard from the nearby restaurant... she stops and says "Two seconds, let me get permission" and gives you a call while he stands there and waits?
If this permission (which makes me shudder) needs to be given at a specific point and in a particular way you guys need to talk unambiguously about it.
Me: male, 40, straight, single