Former China tour guide Yang Yin may have already been convicted and jailed for cheating wealthy widow Chung Khin Chun of $1.1 million, but one person still blames herself for what happened.

Madam Chang Phie Chin, a close family friend of Madam Chung, told The Sunday Times yesterday: "I was the one who introduced them to each other. If they had not met, maybe all these things would not have happened."

Madam Chang, a retired Chinese language teacher who is now 87, first met Yang in 2005 during a tour to Shanghai, China.

They kept in touch afterwards, and Yang would visit her whenever he was in Singapore.

On one such visit in 2006, Madam Chang introduced Yang to Madam Chung and her husband, Dr Chou Sip King. "Yang said that he liked paintings so I took him to visit their private art gallery," she said.

Madam Chang was then living with Dr Chou and Madam Chung. The couple, who were childless, had invited her to live with them in 2004 so that they would have each other's company in their old age.

Madam Chang, who is unmarried and has no relatives, agreed as she had been friends with the couple since 1958 when she used to visit Dr Chou's clinic in Upper Serangoon Road.

After Dr Chou's death in 2007, both Madam Chang and Madam Chung decided to tour Beijing and they hired Yang as their private tour guide. "It was a mistake," said Madam Chang.

After the tour, Yang kept in contact with both women.

A year later, in 2009, he moved into the Gerald Crescent bungalow. He was granted an employment pass to work in the music school he had set up using the bungalow's address. It was later found that the business was a sham.

"Yang thanked me for being his big benefactor," said Madam Chang. "Thinking back now at what he said, my heart really aches."

Madam Chang said that she tried to warn Madam Chung about Yang when he started asserting control over the household expenses, maids and driver.

She decided to move out of the bungalow in 2011 after buying a Housing Board studio apartment where she lives alone today.

She still keeps in touch with friends in the Gerald Crescent area, including Ms Linda Tan, who lives in a corner terrace house several units away from Madam Chung's bungalow.

Ms Tan, a property agent who is in her 50s, told The Sunday Times that Madam Chang told her about her suspicions about Yang as early as 2009. "There was little that I could do at that time," she said.

After Madam Chang moved out in 2011, Ms Tan tried to visit Madam Chung several times but was barred from entering the house by the maid, who was acting on Yang's instructions. Before, the gate was always unlocked and neighbours were free to visit Madam Chung any time, said Ms Tan.

In November 2012, she spotted Yang at a grassroots leaders appreciation dinner.

Surprised that Yang had already obtained permanent residency when she knew that he was not employed, she wrote to the Immigration and Checkpoints Authority, asking it to review his status.

She also got in touch with Madam Chung's sister Doris and niece Madam Hedy Mok, through Madam Chang.

The five of them met at a restaurant at Changi City Point in early 2014. They hatched a plan to get Madam Chung away from Yang.

On Aug 21, Madam Mok, under the pretext of taking her aunt out for lunch, took her to live with her. Yang, not knowing where Madam Chung was, even made a missing person's police report.

Madam Chung's maid Surti Teguh played a part in Madam Chung's flight. A week before, she packed some of her employer's clothes and passed them to Ms Tan over the gate.

Madam Mok also started a legal suit against Yang, alleging that he had manipulated her aunt into handing over control of her assets through a Lasting Power of Attorney in 2012.

On Sept 2, a week after removing Madam Chung from Yang's care, Madam Mok, Ms Tan and three family friends marched into the bungalow, when Yang was overseas, and told his wife and their two children to leave. The family had moved into the bungalow in 2013.

Looking back on the confrontation, both Madam Chang and Ms Tan wished they had done more to protect the widow, and acted earlier. They also miss Madam Chung.

"If only things could go back to the way they were," said Madam Chang. "If it is possible, I wish I could move back to the bungalow and live with my friend.

"We don't have many years left."