In that scene I cringe when Carrie says to Miranda after she tells her she doesn't like the Russian...'Then don't YOU go to Paris with him" lol - great comeback Carrie.
Honestly, I doubt people like Miranda would actually have a friend would wanna confide in her who's so judgmental and cynical.
but as a friend your job is to support your friend's decisions
Carrie also had a point tho, Miranda's opposition came from a place of selfishness
A simple "i think this is a mistake and i wish you would think about it more, but i'll always be here for you regardless" is sufficient. But doesn't make for good television does it.
Miranda was sometimes too judgmental, even if she had good intentions and was usually right.
Her subsequently falling in love with Steve and marrying him was a mystery to me. To me, they were never a plausible couple.
But my point is that Miranda evaluated her friends' choices from a rational standpoint, but not her own.
With that said I believe it was a tad selfish on his part because he already had one.