In the film Meghan Markle is not invited to Pippa Middleton's wedding but is able to attend the reception after Harry protests. What transpired in real life is unknown, but several British tabloids reported that Middleton did have a "no ring, no bring" policy for guests bringing plus-ones, though some guests such as James Middleton and Princess Eugenie attended with guests they were not married or engaged to. Reportedly, Pippa Middleton extended an invitation to Markle, but she chose not to attend the wedding to not draw attention or attract paparazzi, but did attend the reception.
Queen Elizabeth asks Meghan, "Are you involved with that program The Crown (2016)?" and when Meghan says she isn't, the queen jokingly replies, "Good, then I won't have to throw you in the Tower". This is loosely based on a real-life exchange that Elizabeth's husband, Prince Philip, reportedly made at a dinner in 2017.
When Harry's aide interrupts his blind date with Meghan, his reason is that "London Bridge is falling down". That is an actual code phrase used by the royal family to convey the death of Queen Elizabeth II. Every royal has a different bridge used as a code phrase to convey their death.
There are TWO instances in the film where racially sensitive dialogue occurs (both crucial to the storyline). Both aired uncensored in the original television broadcast, but were censored in the iTunes purchase of the film (One would think it would be the other way around!)