If this behavior occurs only at home, and not in the out-of-home settings (such as neighborhood, school, activities with peers), it is reasonable to assume it doesn't represent an organized emotional or mental health condition. Rather, it can be a function of fundamental temperament and parent/child interaction. If it is in that domain, it's best ignored. That is, do not fuss over her or attempt to intervene when she is crying. Just go about your business, and only interact with her when the crying is over.
The last one was right after I had gone outside to talk to her dad on my cell phone. He had been gone out of town for the week and her aunt told her to wait for me inside...
The one before that was when we were on our way out of town and she fell asleep. When she woke up I had her a pbj sandwich ready and she began the same thing. (She has always loved pbj).
When these crying episodes occur, are they a reaction to some precipitant that you can observe? What sorts of things occur just prior to the crying?