Joined this thread a little late, but wanted to throw in my two cents because my husband and I were married last year in a semi-destination wedding. It was a second marriage for both of us, not that it really matters, I suppose.
Okay, here is my take on things, with the caveat that there is no absolute "right" or "wrong" way to do anything:
It's a bit presumptuous for someone to have a destination wedding that costs a lot, does not provide a true vacation for those attending, and for which attendance is strongly encouraged, without the bride and groom footing all or most of the travel bill. It is absolutely tacky to expect people to attend AND bring a gift.
When my husband and I were planning our wedding, we initially wanted to do a Caribbean destination event. We live in Florida, our families live throughout the country, mostly in California and Michigan, and there was no good place to hold the wedding without a lot of people having to travel. Anyway, as we were going through pricing, we realized that even if we covered a lot of the travel expenses for guests, it was expecting too much of people to travel all that way and still have a fair number of out of pocket expenses... and if we did foot the bill, it would be enormous. So - we made the decision to get married at our home in Florida, which is in a city near an airport with easy access for everyone, and we went to Europe by ourselves for our honeymoon. We shifted our wedding budget to a family vacation weekend. It's amazing how affordable the wedding itself can be if you want to make it that way. We provided all expenses for our guests, except for a few who were really well off and simply laughed as us for offering.
Anyway, it was the best decision we ever made. It was easy on the guests, they had a great time and a mini vacation, and they were able to afford to bring gifts, which made them feel really good. It was a win all the way around. It was a small wedding as a result, but it worked out so well for all involved.
My point is this: I think that unless they're planning on a true elopement or something close, it is only courteous for the bride and groom to be considerate of their guests. It doesn't sound like your sister is quite there, and I don't think you owe her a gift at all. Your presence at the wedding is more than generous enough, and I don't think you even owed her that, either, given how it was planned. So... if you attend, you are definitely not obligated to give a gift, and if she is disappointed or offended, shame on her.
Hope you have a wonderful time!
All the best,
Katie
