In hybridizing African Violets the dominate color is purple since the original species are purple.

The best she can do is keep sticking pollen to the stigma and cross her fingers. If she wants a certain leaf type or color type she needs to cross a plant that has the color or leaf she want with another plant that she likes. The off spring should have something like 25% of the seedlings will have the right leaf type but may be not the color. Genetics is a hard thing to wrap the mind around.

http://www.rachelsreflections.com/hybridizing.htm

Here is a link that might be useful: Jeff Smith's Hybridizing notes