Police in the border province received a complaint earlier this month from the victim that Hang Thi Su, 66, and her husband Sung Seo Chu, 51, had tricked her and sold her across the border.
Chu was in debt then, and so he and his wife tricked the girl into going to China to work.
They sold the girl to a Chinese woman for ¥8,000 ($1,178).
She managed to escape back to Vietnam last December.
Chu is already in jail with a 16-year sentence for stealing and trafficking minors.
Vietnam reported over 3,400 victims of trafficking between 2013 and 2019, over 90 percent of them women, children and people from ethnic minority communities.
Eighty percent ended up in China, which suffers from a huge gender imbalance due to its former one-child policy and illegal abortion of female fetuses by parents who prefer sons.