This story is equal parts about immaturity and social etiquette. Throwing a party involves a great deal of social etiquette and that can be hard to balance when children are involved. One mother just wanted her son to have a good birthday and thought she had made the right call to accommodated that. Her sister-in-law loudly disagreed.
My (30f) son's (8m) birthday was two weeks ago. He wanted a pistachio cake, but nobody in our family likes it. So I agreed with him that the biggest cake that would be at the party would be a chocolate cake while he would have a pistachio cake saved in the freezer just for him.
The party took place in our backyard, the whole family was there and the kids had a great time. We sang happy birthday to my son and went to cut the cake.