Do you suppose this is a variation on the imaginary friend phenomenon? Sound like a lot of fun. I would suspect she picked up the accent at school. Do you remember me telling you how you once said in Myrtle Beach, "Mama, tah mah shoos." with the most incredible Southern accent that you certainly didn't get from either of your parents? Then we remembered,Kim, the babysitter from Tennessee. And when our neighbor, Rick, went to visit his Southern grandparents and told them it was time to take a "bohth". Where-ever had he picked up such a British accent, they demanded to know.
Fony appears to be on your side re bedtime. Could be a handy ally.