What breeds do you have that lay white eggs?
What breeds do you have that have crests?
What breeds do you have that have feathered legs?
Can you take a couple pictures of the parent birds and perhaps of your other birds?
RIR always lay brown eggs. I suspect there is more to this birds story.
How old is she?
I am a bit confused....the egg she hatched from was white or she laid a white egg?
Does your EE have feathered legs and a crest?
What other breeds do you have?
Are you CERTAIN the egg she came from was from your RIR?