I have encountered a lot of opinions on here regarding weddings and the obligation to go, especially if it is a good friend, family etc.
I have never understood it, considering the many, many posts by people who have to sacrifice, or feel obliged to sacrifice, a lot of money, time or other things in order to attend - because they feel they ought to go, even if it will be very difficult for them.
I hate the idea of foreign weddings as I think inviting a lot of people to an occasion is always going to mean some of them will find it an awkward location, time or whatever, but still feel they ought to support you by attending. Which is nice and so on, BUT if you make it expensive and awkward in other ways such as by taking the whole thing hundreds of miles away from where anyone lives, you are really not going to have a huge number of people who will findit easy. It raises the awkwardness quotient massively.
Therefore I don't think foreign weddings are a good idea. And I don't think the people who have agreed to go, paid loads of money for tickets and then are told 'sorry, it's all off' are going to feel happy about it. Because often they have had to rearrange their plans to fit with this 'happy occasion'. It's perceived as their social duty.
tellingthem it is then still their social duty to suck up the financial loss is really pushing it imo. Though I can see it comes across as grabbing, I am sure they will have felt very uncomfortable asking - and I'm sorry but I do think your sister ought to have already offered to compensate them in some way, even if just a gesture and not the full amount.
I just hate the whole conceptof big weddings actually. I really do. I'd never want one and I don't understand it. No offence intended to people who do.