ST. LOUIS - The young co-creator of a make-believe MySpace heartthrob that led to a teen's suicide took responsibility for her actions Tuesday, publicly expressing remorse for the first time.

Ashley Grills said that she was part of a scheme to win the trust of 13-year-old Megan Meier through a fictitious online romance, and that, indeed, she wrote the final, angry message some claim pushed Megan to suicide more than a year ago.

Grills' story, which aired on "Good Morning America," did not vary greatly from that already told through documents and authorities here.

But it added details and personal grief.

"I'm not heartless," Grills told ABC News' Deborah Roberts. "I do know what I did, and I take responsibility for it every day."

Grills' story comes out now, after she was granted immunity by the U.S. attorney's office in Los Angeles in exchange for her testimony, according to ABC. The office is investigating fraud charges against the Meiers' neighbor, Lori Drew, for using a false identity on MySpace, the online social networking company based in California.

Before Megan hanged herself in her home in Dardenne Prairie, Mo., in October 2006, Grills was an employee four doors down, at the home business of Curt and Lori Drew, according to St. Charles County prosecutors.

The Drews' daughter had been friends with Megan since grade school. The friendship splintered, prosecutors said, and the Drews heard Megan was talking about their daughter behind her back.

Grills, who was 18 at the time, located Megan's MySpace page. Grills, Lori Drew and Drew's daughter created the fictitious boyfriend Josh Evans to find out what Megan was saying, Grills told ABC.

Then, Grills said Tuesday, Megan wanted to meet Josh.

"Me and Lori's daughter were both telling Lori that we thought it was going too far 'cause none of us can meet her, none of us are guys," Grills told ABC.

"And (Drew) was like, it's fine, you know, we can set her up. We can have her go meet him at the mall and go there and just laugh at her," Grills continued. "And I thought that was wrong."

Then, on Oct. 16, 2006, the day Megan committed suicide, Grills wrote a message online to Megan. "The world would be a better place without you," she said then, according to the Meiers, St. Charles County law enforcement, and, now, Grills, too.

The joke had gone too far, Grills told ABC Tuesday.

"I was trying to get her angry so she would leave him alone and I could get rid of the whole MySpace," Grills said.

After Megan hanged herself, Grills said, Curt Drew told the girls to "get rid of" the MySpace page. Lori Drew told Grills to keep quiet.

Now, Grills said, she is angry at Lori Drew.

"Basically she was trying to make me feel like it was my fault and make me deal with everything," Grills told ABC.

None of the parties involved would speak with the St. Louis Post-Dispatch Tuesday.

The Drews have said through their lawyer that Lori knew about the page but did not participate in writing the messages.