I too think you should go for it. That is how new varieties are discovered. I would breed her back to her father. The chick on the other site (yuku or whatever) was an EE of some sort if you looked all the way to the end of the thread, including muffs when it got older. I thought something was amiss with those dark, greenish looking legs on it as a chick. Your hen/pullet is beautiful if you can repeat the coloring or strength it in the offspring.
I also breed rabbits, and I had a chocolate pop up last summer and was titillated over it. I found out that they show up sometimes when breeding "self" colors together, which I had. I wish it was that easy with chickens.