I ditto to Vikki and Christine. Sometimes as brides, we get way to wrapped up in our weddings that we forget that the people around us have lifes too. Buying a house is a big deal and it's probably something that she would want your support/excitment with, just as you want it with your wedding. Take a few days off the friendship to cool down and take a step back, but I think you'll see that she has valid concerns.
I lost my 4 longest/best friends from the JA part of my wedding. All due to different reasons, mostly kids and cost, they just couldn't make it work. I was REALLY disappointed. Even for a while I thought, wow, I see how much I mean to them. But time and actions have shown that I DO really matter to them! They just couldn't make it work for Jamaica. Even if they do have money in savings, they may have plans for it (buying a house), but whatever their plans are, it's their decision and it doesn't necessarily mean that they don't care about you. There just comes a time in a persons life where they have to think responsibly about their own lifes. Not going into debt to attend a friends DW is a pretty smart move if they can't afford it.
I am really sorry that you are so upset over it, but I have no doubts that she feels just as bad for missing your wedding.
Oh, and I would def tell her and her bf/fi/whatever, that they will owe you for whatever money you have put out as this point since they backed out of the plans. Not sure that you will ever see the money, but I do believe that it's their responsibility, since they are the ones breaking plans.