I can now see the bit of blue on her, since she has the fully black eyes I'd say she is a sky blue yellow face recessive pied budgie. If she doesn't keep the fully black eyes and develop the irises then she could be a double factor dominant pied budgie.
She must have other characteristics that make her not have any markings and the surest way of knowing exactly what she is would be to breed her.
RIP sweet Tito (Summer 2008 - January 17th 2013).
You are missed and never will be forgotten.