Sister at ultrasound.... no thank you


So my sister is 7 years younger than me and egaged. She is baby crazy and being so intrusive on my pregnancy. At my last ultrasound (10wks) my husband couldnt go because of work, so I asked my mother to go. I thought it would be something special since this is her first grandchild. My sister apparently got really upset that she wasnt invited! She gave me a hard time about it and then announced that she was coming to my next one (20wks) no matter what.

I tried to explain to her what a romantic event it will be for my husband and I and how having her there would change the special day. She got so offended and said that she'd keep that in mind during her future pregnancy. I said i would never even ask to go as to not take away from the experience from her and her future husband.

Am I crazy here? Would you want a sibling in the ultrasound room with you and your spouse??