The only way you could have purchased 6, for sure, splash and 6, for sure, blue eggs would have been if she has one totally splash pen and one pen with black and splash mixed together because this is the way blue/black/splash works.
Blue x Blue will yield 50% Blue, 25% Black, and 25% Splash chicks
Blue x Black will yield 50% Blue and 50% Black chicks
Black x Splash will yield 100% Blue chicks
Blue x Splash will yield 50% Blue and 50% Splash chicks
Splash x Splash will yield 100% Splash chicks
Blue x Blue will yield 50% Blue, 25% Black, and 25% Splash chicks
Blue x Black will yield 50% Blue and 50% Black chicks
Black x Splash will yield 100% Blue chicks
Blue x Splash will yield 50% Blue and 50% Splash chicks
Splash x Splash will yield 100% Splash chicks