Would you be pissed?

Okay so for context I am 25, will be 36 weeks pregnant at the event and have a nearly 2 year old.

My brother is getting married, exciting times, but it my future SIL is slowly becoming the SIL from hell! This all started when I was pregnant with my first and we found out we were pregnant together, I was excited to share the experience. She took it as I stole the lime light from her because I had more complications. Since then she has been distant from me and tried to get my parents on her side saying "she's not ready to be a mum she's not even married yet or owns a house" (keep in mind she isn't yet either). So my boyfriend and I ended getting married before our little love bug was born and have been happy ever since. Now jump to when I found out I was pregnant I bumped into her on the go get some tests because I was having complications yet again and she found out. Did she congratulate me? Or ask if I'm okay? No she said "oh my wedding!"... WHAT!? she cared more that my due date is close.to her WEDDING. since then she has been getting worse with making jabs at our family. Trying to get reservations of hotels moved as they are having a destination wedding which I am tryiny best to get to. And trying to get my parents, siblings, and myself to stay in the same house as the groom party for the night before (men which drink alot and I have two teenage sisters). I also told her that I have a plan that if I go into labour on the day I will stay for the ceremony (the important part) then I'd have to go as the hospital will be about an hour away, she turns and says "well you better stay for the reception because I'm paying for you to be there".... WHAT??

and Lastly (sorry this is long but u need this rant) we found out the seating plan.... There was discussion with my SIL and my mum about the seating plan where my mum did ask if I can be sat with them as obvious reasons I won't be able to do much and if I need to leave or something is wrong she is right there... She did not like that so instead she sat me (a pregnant 25 year old mother) with the teenagers. Half of them I don't even know and I've been warned are very much into rec drugs and drinking (the wedding is open free bar btw). I don't knowmif she meant this as a slap in the face or not. When discussing it she said and I quote "if people don't like it then they can get over it I want our families to be comfortable and actually talk"... Am I losing my mind? Do I have a right to be pissed? I'm stressed right now because I just got diagnosed with pre-eclampsia and I'm 34 weeks now. Advice please!!!!