48 Hours brought the girls and their mothers to Guadalajara, where local guides, with the help of information from the adoption papers, took them back to the last known address of their birth mother – a woman named Norma De La Cruz.
But no one in this working class neighborhood could tell the girls where to find Norma, so 48 Hours hired a Mexican private investigator, Fernando Molina, to find the twins' birth mother.
Molina gathered the girls and their mothers together in a Guadalajara hotel room for a phone call from Norma. To everyone's surprise, Norma was calling from her car in Los Angeles. And she had no idea that she was about to talk to the girls she gave up for adoption 20 years ago.
When Norma heard the twin's story, she told the girls she was forced to give them up for adoption. Diane decided not to talk to her on the phone.
"She'd rather not meet her. She was like, 'I don't care about her,'" says Adriana. "'I never have, I never will, I don't know what to tell you. I've been there and I saw what happened.'"
Remember that 20 years ago, Diane and her husband had hoped to adopt Adriana and Tamara, when they first visited Mexico. But the adoption lawyer told her Norma would give them just one baby.
"I don't know what her reasonings are, you know, for what she did, why she did it," says Diane, who had no interest in seeing Norma in California.
The girls and their mothers reached an agreement. 48 Hours would fly Norma to Guadalajara for the meeting. But first, Diane wanted to see Carlos Lopez, the lawyer who arranged the adoption, and who, over the years, had become Diane's very close friend.
Diane wants Carlos with her when she sees Norma: "I just hope it's the truth that she speaks and she doesn't try to make up any stories."
For months, Adriana and Tamara thought about what they would ask Norma, their biological mother. "We have a lot of things to talk about," says Norma. "You can ask anything that you want. And I want to tell you the truth."
Adriana asks Norma why she and Tamara were separated. At the time, Norma says she was pregnant and unmarried when she agreed to the adoption. She says she changed her mind, but claims lawyer Carlos Lopez threatened her: "He told me I had to do what I had signed on the paper or I, and all my family, were going to be in jail."
Lopez denies that this ever happened.
When Norma signed the adoption papers, she agreed to give up just one baby. She didn't know she was having twins. After she gave birth, she claims Lopez convinced her it would be better for the twins to grow up together. She said she believed that her daughters were together, in San Francisco with a Catholic family.
But Lopez showed us documents signed by Norma that he says proves she knew her daughters were going to be separated.
"This is a big lie. A big lie. This paper is fake. I don't know how much money you pay for this paper," says Norma. "The reason I gave you my other baby was so that they would be together."
"I told you with another good family. I told you it was too late for the same family. I told you," says Lopez.
"As a mother, I would want to see them together. But for two weeks, where was Tamara," asks Diane, who says she didn't expect the reunion to end up like this. "I wanted answers. I wanted to know why did she have a good reason to separate them? And it's not. It just seems like a lot of lies going around."
But Judy's not so sure: "When my husband and I went down to adopt, we thought everything was ethical, and I want to think that it was, and I don't know that it was."
As for Norma, she's just happy her girls are alive: "Perhaps to them, I'm not their mother. But to me, they are my daughters."
The only people not emotional about the meeting were the two people who you would think would care the most. "It's not about what happened or you know, who's right or who's wrong, because it's not gonna change anything," says Tamara.
"Whatever happened happened," adds Adriana. "It doesn't change what I am now."
Four months later, in New York, the girls have emailed Norma, but have no plans to see her.
They've learned one thing from their incredible journey. "Anything's possible," says Tamara. "The minute you get comfortable in your life, it's gonna change."
"When you're meant to meet up with someone, whether it be like a relationship, a friend or a sister, it's gonna happen whether you want it to or not," says Adriana. "And people don't like to think like that. They like to think they have control in every single thing in their life, but it's not … To a certain extent, things are always planned out."