Moreno also called on Farc fighters to follow her lead and surrender to the Colombian military.
"To my comrades: Change this life that you are leading in the guerrilla group and re-enter society with the government's reinsertion plan," Avila told a news conference.
Moreno had been accused by the authorities of a series of deadly attacks and kidnappings in the province of Antioquia where she commanded part of the Farc's 47th front.
She said she had been cut off from the main front in the area for the
past two years, and had not had been in contact with the group's
seven-member ruling secretariat during that time.
Alvaro Uribe, the Colombian president, recently said that he would guarantee Moreno's safety if she surrendered.
The Revolutionary Armed Forces of Colombia (Farc), which has been fighting the Colombian government for decades, has suffered a series of setbacks in recent months.
On March 1 Raul Reyes, one of the group's top leaders and a member of its seven-strong ruling command, was killed in a controversial cross border raid in Ecuador by Colombian forces.
A few days later Colombian authorities announced the death of a second member of the command, Ivan Rios, who was reportedly killed by his own men.
News of Moreno's surrender came after Interpol, the global police agency, said on Friday that documents on laptop computers found following the attack on the Farc rebel base in Ecuador that killed Reyes were not tampered with.
Colombia alleges the documents show that Venezuela and Ecuador aided the group, but both nations say the claims are a US-backed smear campaign.