No breed, most cats are not of any particular breed. An fact very few cats are are of a certain breed something like only 3% of the entire population. She would be classed as a beautiful domestic shorthair. Her colour is a tortie ( tortoiseshell ) and white.
I would guess a Short Hair Domestic because that is the most popular breed in felines! Shes a very beautiful calico! Mine is one too and i never get tired of it!