Jelouse sister

My sister can't have kids, well has been trying and by trying I mean has sex with her hubby once a month and whinges about it!!! So I have a twin she has x2 babies and I'm 30 weeks pregnant we are 2 years younger than our older sister, anyway long story short, ever since I fell pregnant and the whole way through my sis pregnancies she is just a really mean bitch and treats us like shit!! I'm soo over it!!! Grr just had to have a rant my twin is over  it but she's trying to stay mutual and not get into the arguments :-/