I think it is harsh to lay into a person with no children for inviting someone to bring their child along.
There's a country song that outlines how meaningful it is to single parents when potentials include the children in the invite. The dad he didnt have to be or some such.
Anyway-it is valid to express why as parents we may say no. But no cause to be unkind. She invited. The. She asked for enlightenment regarding the situation. If all people were so motivated to understand those who differ from them-how much nicer the world would be.
"Love As Thou Wilt"