The 62-year-old multi- millionaire's former personal assistant, Gill Bridge, told Liverpool Crown Court the blonde teenage model had been his girlfriend, and would regularly share his hotel room during business trips to London.
Father-of-five Oyston denies raping the girl when she was 19 and raping and indecently assaulting another model, aged 16, in the bedroom of his country mansion, Claughton Hall, near Lancaster.
Mrs Bridge - now managing director of Blackpool Football Club of which Oyston is chairman - said she first saw the girl at the Midland Hotel in Manchester, when she had been working for Oyston for a couple of months.
"He had obviously met her before because she put her arms around him and kissed him on the cheek. She embraced him."
She confirmed taking telephone calls from her for Oyston at his offices, and that Oyston had girlfriends during the time she was one of his personal assistants.
"Obviously we tried to keep it as discreet as possible. I probably knew more than the other two because I was away on business with him more and saw him more on a social basis than the other girls did."
Mrs Bridge claimed the model would share Oyston's room on business trips to London's Royal Trafalgar and Park Lane Hilton hotels.
"She was quite flirty with him. He was perhaps a little more reserved. It was obvious that she was attracted to him."
She recalled on one visit someone asking her: "What do you see in a chap like Owen?" and claimed she had replied: "I love him."
Mrs Bridge confirmed to Mrs Helen Grindrod QC, prosecuting, that she was still employed by Oyston and was loyal to him. She denied she had ever been the model's friend.
Mrs Grindrod asked: "What you have done is to put a slant on the facts to show that she was having an affair with him?"
Mrs Bridge replied: "She was having an affair with him. She is putting a slant on my involvement because it suits her alibi."
Later, Christopher Cox, a labourer, told the court he had had a relationship with the model lasting for a couple of weeks, during which he made love to her twice in his bedroom at his parents' home.
He claimed he had been mistaken when he made his original statement alleging that this had happened in 1988 - before the alleged rape in 1989, when she claims to have been a virgin. He said he now realised that they had met in 1988 but had made love to each other in 1990.
The trial was adjourned until tomorrow.Reuse content