Daughters who are sensitive... they hold it together in the outside world but when they get home (the "safe" place to be themselves) they let themselves go and show their frustrations and anger about. I'm sure you know this already. But more than anything at this point in time they would like someone to tell them they are still lovable and wonderful.
Also, many gifted girls are very sensitive. But yes when hungry, lack of sleep, or tired, can get very irritable. She doesn't want to be this way but probably doesn't know how to help herself.
My daughter used to melt down almost every evening on the way home from day care. And this was the most loving day care I've encountered --- families don't leave unless they move. My kids (5, 8 & 10) still love to go during school vacations.
When DD was 2-3, I'd load the kids into the car, and she'd be melting down by the time we'd arrived at the light at the expressway. This light is all of 60 seconds from the day care provider's house.
The day care provider told me once that this is common with kids ---just as Jesse said, they have to hold it in all day, and then they melt down when they feel safe. She told me that some of the school-aged kids who came to her house after school would have occasional meltdowns at her place because they felt safe there.
I guess it's a venting mechanism?
I'm teaching her to say "I am frusterated because..."
I say this to my kids too. I always tell them that it's okay to feel angry or upset or whatever. It's how you DEAL with the feeling that's okay or not okay.
FWIW, my mom used to tell my eldest sister to throw a shoe at the garage to get it out.

It helped.
Val