Meghan has been going by her middle name her entire life. I don't see that changing. On the wedding day we will hear "Rachel Meghan" but that will be it. KP announced her as Meghan so that is how she will be addressed.
I believe it's been indicated by Meghan herself that her first name Rachel was used for a time when she was a child in school. I'm not sure when she began using Meghan only, possibly in high school. She was called Meghan by her parents, I think. Although Meghan's mother Doria has always affectionately addressed her as 'Flower.'
It happens sometimes that a child's first name is used in school, while they're called by a middle name or a nickname at home. I have a nephew who doesn't generally use his first name, as he was always called by his middle name among family and friends. However, his first name was used in school.
Meanwhile, I've been meaning to post here in reference to comments by
@Zonk in another thread about Meghan's mother's family being from the South. Actually Meghan's mother Doria was born in Cleveland, OH (but as Meghan indicates in the video linked above by
@ACO) her mother's family moved to L.A. shortly after her mother's birth. So Doria grew up in L.A., and she eventually attended a desegregated high school.
Doria's mother, Jeanette Arnold Johnson Ragland was born in Cleveland. And Jeanette's mother, Netty, (Meghan's great-grandmother) also grew up in Cleveland, although sources have not provided much information about Netty's family background. It's possible that Netty or her parents migrated to Ohio from the South. The information and photos sold to
The Daily Mail by Meghan's uncle Joseph Johnson do not provide a maiden name for Netty, nor any detailed information. It is noted that Netty worked as a lift operator in a hotel and she married a bellboy named James Arnold, later giving birth to Jeanette. Meghan's grandmother Jeanette was married twice. Alvin Ragland, Jeanette's second husband, is the father of Doria. Interestingly, similar to Meghan, Doria has two older half siblings, although they are not as distant in age to her as are Meghan's two older half siblings.
In their initial 'genealogy' reporting,
The Daily Fail reported inaccurately that Alvin Ragland's second wife, Ava Burrow, is Meghan's grandmother. That's not true. More information continues to be revealed. According to a 11/27/17 report in
The Times (UK), Alvin and Ava had a child together who is about two years younger than Meghan, and thus is another uncle (Doria's younger half brother). His name is Alvin Joffrey Ragland, and he's a graphic designer, who is said to be close to Doria and Meghan, so perhaps he will be invited to the wedding.
Here's an interesting clip of Meghan advocating for diversity and for inclusiveness for women. This is the kind of outspokenness that she will seemingly be limited in expressing as a member of the British royal family: