She's been torn away from everything she has ever known in her short life.
Been in a car, (not the most fun things for a puppy. Later will probably love it)
taken by strange sounding and smelling people.
To a new house that has no familiar places or smells.
Give her a couple of days to acclimatise.
Yes she'll be off her food. She's scared and doesn't know what other NEW stuff is going to happen.
She just wants somewhere dark,warm and quiet. To chill and process all these new experiences.
Once she feels a bit safer she'll start to poke around and explore, and her appetite will come back.
As the other guys have said, plenty of water, time and patience.