Background. DSis is 3 years younger than me and always been difficult and competitive. E.g. When I got engaged she wa jealous and got engaged 2 months later and organised her wedding in the same church with reception at mum's home too and most of the same guests 10 weeks before our date. Our mum is very family centric and would love us to be closer but always makes excuses for DSis behaviour.
She now has 2 DC , I am godmother to DD 1. DD2 is 10 months. I am 38 weeks with DC 1. I have been asking for months when her DD2 christening will be. She did not want to do summer holidays as some of her friends might be on holiday. September was out because she was away for a week and had left it too late to organise and December was too near christmas. She lives 2 hours drive away. I warned her that I would not be able to attend for 3 weeks before and after my due date when we spoke 2 weeks ago. Yesterday mum told me that she has planned christening 6 days after my due date. Mum suggested that I might be able to go but accepted my decision not to.
I'm feel that sis is being selfish. My mum had agreed to come and stay for a week after our DC is born to help and is really excited. Chances are that she will be in the awkward position of choosing helping me / coming to meet new grandchild or going to DN's christening and helping sister prepare food etc. If baby is born within a week of due date my brother who lives 4 hours away will also be very busy / struggle to go to christening and visit us. AIBU and should I tackle her about this?