The 61-year-old touched down at Heathrow on Wednesday lunchtime amid growing speculation that she will be the one to walk her daughter down the aisle in Windsor, with ex-husband Thomas Markle reportedly set to miss the event after undergoing heart surgery.
Both had been due to arrive in the UK this week to spend time with the royals ahead of Saturday, including the Queen, the Duke of Edinburgh, the Prince of Wales, the Duchess of Cornwall, and the Duke and Duchess of Cambridge.
Ms Ragland, a yoga instructor and social worker who met Prince Harry at the Invictus Games in Toronto last year, was whisked through security at Heathrow’s VIP Windsor suite after her 10-and-a-half-hour flight from Los Angeles, where she lives.
She was met by Ms Markle’s personal assistant, Amy Pickerill, while Prince Harry’s aides were seen helping with her luggage, including the Burberry garment bag she was spotted carrying out of her LA home on Tuesday.
The future royal mother-in-law is believed to have left Heathrow in a Jaguar estate, which is part of the royal fleet, accompanied by police cars.
She is expected to have been taken to see her daughter and future son-in-law before meeting other members of the royal for the first time before the wedding.
On Tuesday afternoon she was seen leaving her LA home dressed casually in a pair of loose trousers, a t-shirt with a drawing of a dog, a blazer and the Burberry bag.
Photographers later spotted her checking in at the exclusive Private Suite at LAX airport, used by celebrities and wealthy travellers.
Earlier this week it was revealed that she will stay with her daughter at the Cliveden House Hotel, roughly nine miles from Windsor, on the night before the wedding.
Prince Harry will stay at the Dorchester Collection’s Coworth Park in Ascot, Berkshire, with his brother and best man Prince William.
Forecasters predict that it will be warm and sunny on the big day, which is expected to see 100,000 people from around the world descend on the town.
The likely absence of Mr Markle, 73, was first reported on Monday by TMZ, which said he had decided not to appear after being left “deeply embarrassed” by the release of pictures that appeared to show him colluding with photographers.
It forced Kensington Palace to make the unusual move of addressing the story via a formal statement, which acknowledged Meghan was going through a “deeply personal moment” and pleaded for “understanding”.
But the most recent indication from the former Hollywood lighting director is that he will not be making the trip, having been booked to go into heart surgery in Mexico, where he lives.
More from Royals
Harry and Meghan’s secret codes revealed
Royal wedding: Prince George and Princess Charlotte among page boys and bridesmaids
Palace plea for ‘understanding’ as Meghan Markle’s dad may not attend wedding
Royal wedding 2018: Meet Prince Harry’s ‘Glosse Posse’
Royal wedding 2018: Full schedule of Harry and Meghan’s big day
Down it! Memories from reporting on Prince Harry
:: Sky News will broadcast live in Windsor the week before the royal wedding with all the build-up to the big day, with exclusive live coverage of the wedding in UHD in a special programme from 9am to 3pm on Sky News and Sky One on Saturday 19 May.