I think she's jealous of my pregnancy?

Im now pregnant with my second baby and i feel my step sis-in-law is jealous of this. she used to be alright towards me but since my husband and i announced our pregnancy she's been really off and cold towards us, ignoring us at family gatherings and being pretty rude in my mind. She's also pregnant with her second too, a few weeks behind me and my husband says she's being like this because she likes to be the centre of attention and gets the impression she wanted everyone doting over her during her pregnancy and now because we're gonna both be pregnant at the same time she's annoyed that we've basically stolen her thunder (which is stupid as i dont like being made a fuss of and we conceived first so its not like we got pregnant just to spite her - nor are we those kind of people) anyway im not sure how to deal with this, never been through anything like this before n its getting me down as its making social family occasions quite awkward, any advice would be great thanks. xx