Gender Reveal Ruined??

Even before I was pregnant I knew that I wanted to have a gender reveal, its something so important to me. its finally the time that we can find out the gender reveal so it is planned next weekend, a few days after the ultrasound (fingers crossed they can tell lol). I've always had a vision for it, cute decorations, a small group of people that matter most to me and him, everything perfect. I tend to envision things before hand and that's exactly what I want. I bought all of the decorations and sent out invitations to the people I'm closest to, I did not invite my whole family, just my parents, one aunt, and my sister because they are the only people I'm close to. on his side I invited everyone he requested. it's at 3 so I only wanted dessert type foods, not a full meal, just things to snack on, and most importantly I can make pink and blue.

today I've been informed that were expecting another 15-20 people. his mom invited his whole family. people I've never met or even heard of. and she's planning on bringing a full dinner. I'm very disappointed. this isn't how it was supposed to be, this isn't how I imagined it, or what I wanted.

I wanted 20 people tops all that I love, just together for an hour or so to find out the gender of the baby. not 50 people that I barely know, that my boyfriend barely knows, having a reunion for multiple hours, a full meal.

am I being selfish? or did she have no right to invite so many more people without even consulting me first? I really feel like my gender reveal is going to be ruined because this isn't what I wanted. i didn't want to make a big deal and have everyone come and bring gifts and such.