Ms Markle's mother, Doria Ragland, will meet the Queen for the first time at Windsor Castle later, accompanied by her daughter and future son-in-law.
Ms Ragland has already been introduced to some of the Windsors - including Prince Charles and Prince William.
It remains unclear who will walk Ms Markle down the aisle of St George's Chapel as her father will not attend.
Ms Markle released a statement on Thursday confirming her father would not attend the wedding and saying she hoped he could be given space to focus on his health.
Ms Markle and Prince Harry were in Windsor on Thursday to prepare for the big day.
Rehearsals took place for the ceremony and for the military procession around the town.
The couple were seen being driven along the procession route, accompanied by a police escort.
Other members of the Royal Family are also in Windsor ahead of the wedding, including the Duke and Duchess of Cambridge and Prince of Wales and Duchess of Cornwall.
Ms Markle's mother met William and Catherine and their eldest children, Prince George and Princess Charlotte, at Windsor Castle on Thursday afternoon.
And she took tea with Prince Charles and Camilla at Clarence House in London on Wednesday.
Meanwhile, further details on the wedding cake have been revealed.
Its baker, Claire Ptak said it would be presented in a "non-traditional" way, displayed in a special "installation".
The layered lemon and elderflower cake will be served to 600 guests at the afternoon reception at Windsor Castle.
The owner of Violet Bakery in east London described the cake as "a slight shift from tradition".
She has been baking with the help of a team of six people for five days in the Buckingham Palace kitchens.
Some 200 Amalfi lemons are being used in the recipe, as well as 10 bottles of cordial made using elderflower from the Queen's Sandringham estate.
She has not made a back up cake in case of a disaster - "It's cake. It can't go that wrong," she said.
Thomas Markle's absence leaves a question mark over who will walk Ms Markle down the aisle.
Her mother is one option; Harry's father, Prince Charles, is another - or she could choose to walk alone.
Mr Markle had been due to arrive in the UK in the days before the wedding but became caught up in controversy over the apparent staging of photographs with the paparazzi.
Ms Markle will have 10 bridesmaids and pageboys, who are all under the age of eight.
She decided against having a maid of honour, saying she wanted to avoid choosing between her closest friends.
The rehearsal of the carriage procession in Windsor on Thursday drew hundreds of children, parents and pets keen to embrace the party mood.
It went largely without a hitch - although some horses were seen veering out of line.
About 250 members of the armed forces are expected to take part on Saturday.
With just one day to go, BBC Weather is forecasting a sunny, breezy day for Saturday with temperatures reaching 21C (70F) in the late afternoon.