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 and every kid (8 kids all under 9). The adults would get a 2-pound cake to be shared. I elaborately decorated the cupcakes and made sure I made enough. I didn’t have the energy to make extras.<br><br>On the day of the party, one of my cousins brought her boyfriend and his kid Gina (7f) over unannounced. Gina saw the cupcakes each kid got and wanted one, too, so my cousin brought her to me to ask for a cupcake. I apologized and told them that all the cupcakes were spoken for and that she was welcomed to have a slice of the 2-pound cake as it was the same flavor.<br><br>Gina said she wanted the pretty cupcake. My cousin then said I should just give her one because she was sure at least one of the kids would not show up. Again, I refused, saying that I promised all the kids a cupcake and would feel awful if anyone had to miss out on the promised cupcake. My cousin then walked away with Gina.<br><br>She was right though as one of our cousins’ girl, Amy (8f), was sick and couldn’t come. However, her dad and older brother did and the brother asked if he could take the cupcake back home to Amy and I said yes. <br><br>My cousin and Gina were in the kitchen when I brought the cupcake inside to pack it up for the Amy. When they saw me packing the cake they asked about it and I said it was for Amy who was sick.<br><br>Pictures from the party were recently posted. Many parents posted pictures of their kids with my cupcake. My cousin sent me a message, telling me that Gina was really upset that Amy who wasn’t even at the party got a cupcake while she didn’t. She said I was AH for hurting a little girl’s feeling.<br><br>I think I did the right thing giving the cupcake to Amy as I did promise her one. Still, Gina was right there at the party. AITA?