I did that once. Trust me it was exactly the same pattern you have discussed and we are not on speaking terms today though she finally ended up marrying someone else. May be there are other reasons too , but I guess that well meaning advice was one of the nails on the coffin. But, you know what, that is what friends are for. It all depends on your intentions. Did the advice come out of malice or that you chose what was best for your then mate?

If I had a friend, I would want them to be honest. I wouldn't judge them for it. I wouldn't let it color my rationality specially if I believe that my partner is good for me. However if you are having reasons to bitch about your partner to someone else, may be something is not right already. What if tomorrow the domestic abuse turned so severe that you lose your friend or something of that magnitude, would you then forgive yourself? To me, you did the right thing. Friendship isn't about diplomacy. You still support them in whatever decision they take despite, but you owe may not be your friend, but your friendship an honest answer.