Tammy, I must say I can relate. My sister was the same way when I built my house. She's older than me, and I think she gets jealous easily. I think the fact that I reached some milestones before she did bugged her, really bad. She also wanted a DW but couldn't afford the AHR and her FIL's weren't too keen on the idea, so she didn't have one. So, maybe your big sister is just jealous of you. Hopefully she'll be like my sister and realize that her life is pretty amazing and that there is nothing to be jealous of. Everyone lives their own life.
Good luck