Tough situation

So I am almost 8 months pregnant with my first child... A girl. During the beginning of my pregnancy my sister and I had a falling out and she has always been super jealous and negative and mean and ruins every family function and so on. During my pregnancy I found out that I have a 99% chance of having my baby girl be born with Down syndrome... It was a tough time and my best friend was there for me every step of the way for emotional support as I got used to the idea of possibly having to raise a daughter with special needs. Now I am over the shock and absolutely fine with whatever God decides to give me I am ready for and will love her. My sister and I just started talking about a month ago... There is no emotional support or anything from her just negativity and judgement. She never asks how im feeling or about the pregnancy if I bring it up she changes the subject to be about her and her dating life... She's my older sister has no kids and isn't married. My tough situation is that I am going to christen te baby soon after both and I want the God mother to be my best friend. But if I don't chose my sister it will cause world war  3 with her.... She will flip her lid. But I seriously don't want my sister being the God mother she wasn't there for me when I needed someone and all she did was cause stress and fights at my baby shower and my best friend was so helpful and did so much with barely being asked. I really want my best friend to be te God mother but I am afraid of the consequences... Everyone says she's your only sister you have to make her the God mother but I really don't want to but is it worth the fight? I could just say I asked my best friend when we weren't speaking and I can't unask her. My friend would go along with it cause she knows how she is. My sister literally stared at me with hatred at my baby shower everyone noticed.. Also made fun of a lot of the beautiful gifts I got for my daughter... Like she can't stand that I have a family and I am married and she can't even get a boyfriend. But why should I be punished for that? Any advice? 😁