The stage of "Britta"...

"Britta, you're the best mommy I ever had!" 

-Ari (2 years old)

"Um... Britta? Wouldn't you be embarrassed if the high school boys saw you dancing like that? I would be embarrassed for you." 

-Ari (4 years old)

Ari has called her mom by her first name since the age of 2.  In the beginning, her parents found peace with it based on the following three beliefs 1) she was not doing it to be bratty or launch a power struggle, 2) it seemed remarkably consistent with her personality, and 3) it was probably just a stage and she'd be over it soon enough.
When I say "found peace with it" I should clarify that this did not mean her mom didn't struggle with it at times. As the years passed and the "stage" persisted, Britta had her moments of doubt and was forced to ask herself some tough questions.  For example, was she really the pushover mom the old lady in the store seemed to view her as when she graciously shared the punishment techniques she would have used to "put a stop to that" when her kids were young?  Then there were the times when Ari's mom realized how much worse "I don't think so, Britta!" sounded coming out of the mouth of a 2 year-old than "No, Mommy!" would have sounded if she just talked like other kids.
But then there were the times she couldn't resist. Like when she'd arrive to pick up Ari from preschool and one of the kids would yell, "Ari, your Britta's here!" and Ari seemed so proud that while every kid in the class had a "Mommy," only she had a "Britta." Or when Ari would introduce her mom to a new friend and excitedly announce "This is my Britta."
And now it seems that the stage is finally coming to an end. Ari calls Britta "Mommy" lately and Britta loves how it sounds to be called "Mommy" by the coolest girl she knows. And she's grateful that while other moms get to be someone's mommy only she ever got to be Ari's Britta.