I have to agree with lotsofmagnets:
If you're really opposed to this, why *would* you go to the wedding? To me the people at the event are there to celebrate with you, and enjoy your special day together. If you participate, you agree with the whole thing.
If it's gonna even cost you a serious amount of money & holidays on top of your gift, then it better be a very good buddy of mine before I would attend.
However, I don't see where he's asking you to be a friend and be there for him even in spite of...?
In all fairness to his buddy, I'm wondering if he even knows you have a problem with his choice.
And as an added: you've seen this girl one or two times, and went out with her 1 night...
Flakeyness and golddigger both seem to me like the things you can "figure out in 2 minutes tops!".
These traits themselves are flaky... Depending on her mood she may have exhibited this, depending on if she felt at ease with you, depending...
Like Jewels said: he's spent a few years and has decided something based on this experience.
If you value his friendship still, then I would give her some more time and benefit of the doubt.
But I still wouldn't go to the wedding if it's in Italy
