No, she is not going to be ruled a British citizen. She was born in California and the law of the land long before she was born was that she is a citizen.
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There is a world of difference between a “citizen” and a “natural born citizen “ as the Constitution demands. BOTH of her parents must be US Citizens at the time of her birth in addition to her birth on US soil in order to be a NBC.
Yeah, and as a little girl her mother took her to Canada, where she received all her schooling. Mother never became a naturalized American. She may have become a Canadian.