I think it was on purpose. Their way of telling you they don't like your hair without addressing you directly. it was a small party. Was anyone else a big curly that could have sparked the conversation? If not they intended you to hear and they brought up the not wanting their daughters to have curly hair thing because your daughter was there with curly hair.
I have had people do this to me before but that was back in high school because it is very childish. I don't consider someone "educated" just because they have some college degrees. These people are rude, small minded and ignorant.
"More people would learn from their mistakes if they weren't so busy denying them." - Harold J. Smith.