Without a known pedigree she is considered a Domestic Shorthair. I don't see any features that jump out to me as being any particular breed. Her color/pattern looks like Brown (black) Mackerel Tabby and White. She might possibly be Classic tabby instead of Mackerel, I cant' tell without seeing more of her sides/back.
She looks like a dlh medium hair maybe to me, with a bicolor harlequin pattern and she is a brown tabby, i also cant tell if the tabby pattern is mackerel or classic, classic has a Bullseye ipin the center of the side usually while mackerel has mostly stripes radiating out from the spine.
What a cutie