This is essentially it:
On 8 November 1993 Prince Edward arranged a date with Sophie Rhys-Jones. He had forgotten that he was due to have a late lunch with his parents. the Princess Royal and Tim Laurence at the same time, after the centarph service. Realising the mistake on the day he asked the Queen if he could bring Sophie to the lunch.
In the weeks that followed the Queen had related to the Queen Mother about Edward's girlfriend, famously refering to her as "unnoticable in a crowd,". She also spoke to his ladies in waiting and other famly members and friends. The Queen Mother desperately wanted to met Sophie and arranged a family lunch after Sunday service with the exact purpose.
After the lunch the Windsor men retired outside with their refreshment to overlook Prince Andrew's new car. When Diana arrived early returning William and Harry to their father and to spend time with the Queen. Leaving the boys by the men, Diana went inside, asking one of the couriers on the way if Sophie was with the Queen at the time, when they replied yes, she replied that she wanted to see who was replacing her.
By some accounts of the story Diana arrived when the Queen was going over the family album and in the middle of Princess Anne's story of something that happened while she was in Australia, while others note that Anne has already excused herself and was already on her way out.
Diana apparently say down besides Sophie and began what Princess Maragaret described as and interogation.
Diana commented about Sophie's skirt, saying it was nice for Marks and Spencers
anyway and that must be expensive on her wages. She then stopped and asked with Sophie earned a salary rather. She then asked what Sophie's father did, when Sophie answered that he was retired, Diana replied that he must how be hard up for money. Apparently this is how it continued for almost half and hour, most of the questions revolved around how pooor and common Sophie was. Sophie then asked the Queen if she could leave and left the room. The Queen Mother apparantly told Diana off and when Diana tried to explain her behaviour, Princess Maragret remaked she had been a common b--ch, at which Diana left the room.
Upon leaving she ran into Andrew, Philip and Edward who were going upstairs, Diana told them that Sophie was not longer there. When the Duke of Edinburgh asked why she had left early, she answered that she was complaining of women problems and decided to leave. Edward went up to his apartment to find Sophie crying packing her things. He must have conviced her to stay as she didn't leave. The next day, the Queen and the Queen Mother apolgised for Diana's behavour.
Diana went home and phone Andrew Morton whom had already been told that Prince Edward had a new girlfriend and was eager for more information. She told him that Sophie was a carbon copy of her and that the monarchy were also grooming her to replace her.