AITA For not giving a cupcake to a child who is not originally on the guest list

I (24f) recently returned to my hometown after being away for college and work. My grandma often hosts potluck party where her 3 kids and their families can hang out. I am a pretty good baker and the couple of times I brought baked goods over, I got lots of compliments especially from the kids. <br><br>For the potluck we had last week, I had promised to make a cupcake for each of the kids (8 kids all under 9). I made decorations with each of their names on it. Some were themed after their favorite cartoon character. <br><br>I made exactly 8. I didn't have the energy to make more and brought the exact amount thinking that it was enough. <br><br>On the day of the party, one of my cousins brought her boyfriend and his kid Gina (7f) unprompted. Gina saw the other kids eating the cupcakes and wanted one. But by the time she came to me, all the kids have gotten their cupcakes. I told her I didn't have more left. <br><br>She started whining and my cousin tried to help. She brought me to the kitchen saying we could take off the custom decorations from hers and give the bare cupcake to Gina. I refused saying that's hers and I worked hard to make the decorations. <br><br>Gina kept complaining and my cousin suggested I make a new one. Again I refused saying I was too tired and didn't have the energy to make a whole new cupcake (it was 3 hrs to make 9 cupcakes). <br><br>Her boyfriend then said I was being a bitch for not giving a cupcake to a little kid and that I was being a jerk for not making a new one considering I was the one who brought the cupcakes.<br><br>The party was pretty awkward after and some of my relatives had been giving me looks. I feel like I might have been an asshole but I'm not sure.