I have a cousin that will NOT add me on facebook, what can I do?

She added all our other cousins and family members and for over a year I have been requesting her and messaging her. I did not say or do anything to her. I had her added and then lost her and now she will not add me back. She is kinda snooty acting at the family reunions, I wonder if it is because I dont' look like a model or have loads of money or what. ugh She will not tell me why she won't add me, all I wanted to know was why? I don't care about being added I am just afraid I made her mad or something and didn't know it. gee whiz. any advice would be helpful. thanks.