Why in the heck would this girl do something this disrespectful?!?

Hi guys, the other day, I was at a birthday party for a family member of mine... they had invited basically everyone they knew, over 100 people, including a girl, I think she is 12, from my church. Well, while there, I saw her peeing behind a car in the yard of my uncles! Why would she do this?! There were 2 bathrooms inside the house... clearly pointed out, which were both empty, as when i saw her, I had just walked out of the house... so my question is, why would she just not use the clearly marked restrooms inside the house, but have so much disrespect and pee in the yard of someone who graciously invited them to a party?!