I REALLY NEED YOUR HELP, I'M MAD, MAD?

My nephew is getting married and I was invited to the wedding. My brother and wife told me I could stay there. I was going to sleep in sofa, suddenly my sister-in-law's cousin decided to to fly to N.Y. and they offered the sofa to her leaving me on the air. I could stay with my sister but she is out of state. Now I have to fly from L.A. to N.Y. which it will cost me around $500.00 plus the gift. I love my brother dearly. I had been sick and I'm doing this as a sacrify since we are the only two in the family who will be there. Now I feel really mad because they have two or three bedroom uptairs but it didn't occur them to fix one of the room for me for a few days. It's always this way, first my sister-in-law, second her family and we come as second hand. Now they rented a room in the hotel for one night where the wedding is going to be and they left the room for my sister-in-law's cousin also. After they made the decision they called us to tell that we could drive there and the cousin was going to stay in the hotel. They could up make arrangement and take two rooms but it didn't occurred to them. I have to spend a lot of money and I don't really want to go, not because the money but the principle. I had been treated as second hand when we are the one who help them when they need some thing. I already bought a ticket ($500.) which it take 5 hours plus the extra time waiting and the incovenience since about 1-1/2 I had a heart attack. I want to cancel the trip because I don't like this b.s. MY QUESTION IS SHOULD I GO TO THE WEDDING OR LET THEM KNOW THAT I'M NOT GOING AND SEND MY NEPHEW THE GIFT. I would appreciate your help asap since I don't have much time. I really, really appreciate your help and how would you feel about this? LOVE YOU ALWAYS.