Is my sister right?

My family and I (husband, our 4 year old daughter and 5 year old son) are going to Disney World next summer. It’s our first time going as a family and we have been so excited. When I told my sister, she wasn’t excited for us. Instead she said that it was rude of us to not invite her 2 year old son to come with us. I explained to her that I personally thought 2 years old was too young to go to Disney and that it was just going to be a vacation for the 4 of us. Nothing against her son, just that this was a special 1st vacation. My sister called me selfish and said I know she’s been struggling for money and can’t afford to take her son on vacation right now. I talked to my husband about it and he said he’s fine with them tagging along. So I told my sister she’s welcome to come but that she would need to pay for her plane ticket and she got angry. She said that I’ve never been a good sister & I’m selfish. I told her we can’t afford 2 more plane tickets or food costa but that we could pay for her and her son’s Disney tickets and hotel room and she said if we can’t afford 2 more plane tickets then we shouldn’t be going at all.

After this I told her she was unbelievably ungrateful and we would be happy to take her son with us so he can experience Disney too and spend time with his cousins but that she was no longer welcome to come. I woke up to 10 voicemail messages of her screaming and crying and threatening to never let me see my nephew again (who she knows I love like my own).

Is my sister right to be mad? She is ruining this holiday for me and my family 😢