She is a beige mosaic. Mosaics come in many different patterns! The other two are either beige mosaic or regular white mosaic even if they have no markings (the difference is if they have a beige or standard gene in addition to a white gene). Sometimes beige mosaics are called Pink Whites, they have their own section under whites at a show.
While mosaics in general are quite common, the half one color/ half white pattern isn't super common but I probably wouldn't say call her rare either. I bet she's a cutie; I would love to see pictures.