There's an old saw: When first we set out to deceive...
I guess that you are learning anew that the easy thing to do often isn't the smartest! But, I believe that you handled it quite well despite being tossed under the wheels of the bus. Is it possible that your friend has her eye on your ex and sort of wants you to move over? Or is she a bit bitched about you having two guys and her none?
I suppose that it makes no difference, does it? Some friends will die for you, some will allow you to do the dying! You know what you are dealing with here.
As for the selection of guys, wow! You are fortunate. I've been the 25yo with the 39ish woman and assure you that it was a grand summer from my viewpoint. Those are memories that will never be "bittersweet".
So...sort them out, enjoy them and don't rush to some sort of permanent hookup. The impulse to exclusive possession is somewhat overdone!