Clean her face with warm water, using kitchen paper or a cloth and not cotton wool as the fibres can get in the eye and cause problems.
Izzy was the only one of mine to stain and , having tried various products, I gave up, just making sure he was clean and dry.
A product (made in the US) that a dog magazine once recommended was Bio Groom's Stain free. At over £6 for a pot the size of an eye shadow pod, plus postage, I decided not to bother. This product is prohibited in UK show rings.
Barbara, Monty, Joly and Teddy.