Am i the asshole if i don’t go to christmas

My sister and I have both struggled with eating disorders our whole life’s. Right now I am trying my best to stay in recovery, as I have two kids & struggling with postpartum depression. My sister in the other hand is very deep in her eating disorder and has no intention of recovery. She lives at my parents and they pay for her life. My husband and I went over to my parents the other day for a family party, and I got so triggered. I have been struggling the past few days since. We are having two big christmas parties at my parents house, one on christmas <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">eve</a>, and again on Christmas. I don’t think I can handle it, the thought of doing that again makes me think the worst thoughts. My kids are the only grandkids, so if I don’t go, my parents and siblings will be so upset that they won’t get to see my kids. I really don’t know what to do.