Some folks are pretty knowledgeable on their own because they study various things...history is something some folks do on their own too. So we really don't know Meghan's knowledge of British history or the BRF ..although I'd say she's been studying up on the BRF and I'm sure Harry and she have talked about the various items.
She's going to have time after they marry too....I would imagine she will get a grace period just as Kate did. I doubt they will be expected to marry and hit the ground running in the manner his parents did.
LaRae
Diana didn't hit the ground running. She also had a grace period. If you look at the Diana's royal engagements thread, they have these listed.
1981
February, 24 : Announcement of the engagement
February, 27 : Visit to Cheltenham
March, 09 : Reception to raise funds for the Royal Opera House
March, 13 : Grand Military Gold Cup
May : Visit to Tetbury
June, 06 : Polo Match
June, 10 : Banquet for the King of Saudi-Arabia
June 13 : Trooping the Colour
June 15 : Order of Garter
June, 28 : Polo Match
July, 08 : Polo Match
July, 11 : Polo Match
July, 12 : Polo Match
July, 24 : Premiere "For Your Eyes Only"
July, 25 : Polo Match at Tidworth
July, 26 : Polo Match at Smith's Lawn
July, 29 : Wedding
November, 04 : Visit to Splenders of the Gonzagas Exhibition
November, 12 : Visit to Chesterfield
1982
March, 04 : Night of the Knights
March, 18 : Cheltenham Races
March, 29 : Visit to Leeds
April, 03: Grand National Horse Races
May, 02 : Polo Match
May, 15 : Polo Match
May, 22 : Polo Match
May, 30 : Polo Match
June, 04 : Polo Match
June, 06 : Polo Match
June, 12 : Trooping the Colour
June, 13 : Polo Match
June, 15 : Polo Match
June, 21 : Birth of Prince William
June, 22 : Leaving the hospital with William
August, 04 : Christening of Prince William
September, 04 : Braemar Games
November, 18 : Banquet for statevisit of Queen Beatrix and Prince Claus of the Netherlands
December, 08 : Visit to the opera
So not much at all. Especially, since I doubt most of those polo matches actually counted in an official capacity. Meghan is not a future Queen so she'll have even less expectations. If she spends the first few years of her marriage focused on starting a family, with the occasional royal duty, then she'll be falling in line with those before her.