Meghan Markle, First Female Mixed Race Woman in British Royal Family?

Meghan Markle will officially become the wife of Prince Harry after a mass of blessing on Saturday, May 19, 2018. This marriage, says many people, a sign that multiracial women can go into the British Royal family.
Meghan Markle is a woman born to an African-American mother and a white-skinned father.

According to historians this is not the first time a member of the British Empire marries a man of African blood. According to historian Mario Valdes, Charlotte of Mecklenburg-Strelitz is a black woman married to George III in 1761 in England as quoted from the Historian page, Friday (18/05/2018).
Valdes mentioned that Charlotte had a relationship with Margarita de Castro y Sousa, a member of the black Portuguese Royal Family.

However, more evidence suggests Charlotte has blood from dark-skinned people from his face. Based on a variety of paintings Charlotte shows his face has characteristics of African descent.

On the other hand, Stuart Jeffries says that there is not much evidence to suggest Charlotte is black. In George III's time, he signed the abolitionist act of slavery. Of course if having a wife who has black blood sparked the debate.

So what did Buckingham Palace think about Queen Charlotte's background? In 1999, a spokeswoman for the Buckhingham Palace said, "This has been a rumor for years, it's a historical matter, and frankly, we feel there's something far more important to talk about."