She told the court that she became a slave to his demands.
The former Manchester United star and ex-Wales manager is on trial accused of controlling behavior and assault.
She testified that he made her feel like she had to do what he said.
All the charges have been denied by him.
Ms Greville said she made a number of statements to police after the alleged assault.
Did you tell the whole truth in your statements?
The barrister inquired about Ms Greville's relationship with the former footballer.
She said that he was playing on her vulnerability.
Two consenting adults, both equally married at the time, who embarked on an affair?
The witness said that the situation she was in with her ex- husband made a difference.
Ms Greville told the court that she wasn't happy in her marriage and that Mr. Giggs was interested in her.
She said she had read about how to win friends and influence people in a book.
She was suggesting there was a psychological game going on.
He asked if it was the case that you only had an affair with Ryan because you were unhappy.
Ms Greville said it was not all one-sided. I was a part of that. There were certain things about him that made me fall in love with him.
Ryan was using psychological techniques on your vulnerabilities. Isn't it just rubbish?
Ms. Greville said absolutely not. He was using techniques. I knew I was vulnerable. I was in a relationship with another person. It is a fact.
She told the court that her ability to interact with her family was affected by Mr. Giggs' alleged controlling behavior.
Ms Greville told the court that Mr Giggs used aggression more as a form of control.
He asked, "Do you think he undermined your confidence, your self-esteem and was unflattering to you?"
On the whole he was, but on the other side it was very different. He would give me something to believe in.
He was not terrible. It was warm. There are two people. His actions undermined my confidence.
The court heard that on the day before the trial began, Ms Greville said she felt like a slave to the man.
She said it felt that way. I would do it when Ryan told me to.
He made me feel like I had to do what he said if I wanted to avoid consequences.
During the relationship, Ms Greville searched for what was happening in her relationship on the internet.
She said that the thing that came up was not coercive. It was very similar to that.
She said she wasn't looking for compensation when the case is over.
He asked if he was kind and loving to her most of the time.
Ms Greville said that they would start with that. For four and a half years he was nice, but for a year and a half he wasn't. It was really bad near the end.
When she returned to Manchester in January of last year, she noticed a significant change after living together for a while.
The abuse became written in messages and emails towards the end of the relationship because Ms. Greville was standing up for herself.
The jury heard that Mr Giggs headbutted her after she confronted him about his infidelity.
She said he had relationships with eight other women while they were together.
She said that the discovery of messages on his iPad led to her leaving him.
Mr Giggs is accused of controlling and coercive behavior against Ms Greville over a two year period.
He is accused of attacking Ms Greville at his home in Greater Manchester on 1 November 2020.