Cry time?

My girl had a sweet friend spend the night last night, and they stayed up SO late.  Now she is more than just a little prickly.  Knowing this, I sent her to bed and told her to read a while.  My secret plan/hope was that she would fall asleep.  Instead she cried because she wants more Barbies.  ? 

She came out after a while and let me know that she had been crying ‘a long time’ over a ‘silly thing.’  When she told me that she was crying over Barbie, I agreed that it was a little silly.  Then she said that she had to cry because she had been crying over such a silly thing.  *sigh*  Why must this cycle of self-berating begin so young??