The worst thing someone you don't like can do is invite you to their wedding. If you choose not to go to their wedding, you still have to send a gift and they win. After all, if you don't like them then they probably don't like you, and they just got a free gift from you and didn't even have to see you at their wedding. And if you decide to go to the wedding for the free meal and drinks, you still have to give a gift, and you also have to spend a lot of money on travel and hotels and so forth. Then you also have to put up with a lot of the person's friends who are just like them. But it's all worth it if it ends up storming super hard on that person's wedding day and you were there to see it.