Old Bailey bomber Marian McGlinchey has pleaded guilty to providing a mobile phone linked to a Real IRA attack in which two soldiers were murdered.
McGlinchey, also known as Marian Price, admitted providing property for the purposes of terrorism.
Sappers Mark Quinsey and Patrick Azimkar were shot dead as they collected a pizza delivery at the front of the County Antrim barracks.
McGlinchey had been accused of buying a mobile phone that was used in several calls claiming responsibility for the Real IRA attack.
She was also accused of aiding and abetting the addressing of a meeting to encourage support for terrorism.
The second charge related to a separate incident at a dissident republican rally in Londonderry in April 2011.
At the Easter commemoration rally in the City Cemetery, she was filmed holding a piece of paper for a masked man as he made a speech, during which he issued threats against Catholic police officers.
McGlinchey, from Stockman's Avenue in west Belfast was already on trial accused of buying the pay-as-you-go mobile phone and was due to face a second trial over the charge related to the dissident republican rally.
However, at Belfast Crown Court on Thursday, her defence barrister asked for her to re-arraigned on both charges.
The 59-year-old was released on continuing bail and is due to be sentenced next month.
Her original trial, which began on Monday, heard that she had links to "dissident republican activity" and must have known that the mobile phone she had bought was to be used to make the call claiming responsibility for the Massereene Army barracks attack.
A prosecutor told the earlier trial hearing that on the day after the soldiers were murdered, a unknown man made a number of telephone calls to media outlets and the Samaritans claiming responsibility for the attack on behalf of the Real IRA.
The prosecutor added that on 8 March 2009 a woman was caught on CCTV buying the mobile phone from a Tesco store in Newtownabbey, County Antrim.
She adding that it was the Crown's case that the woman seen buying the phone was McGlinchey.
The trial heard that the mobile phone was first used to claim responsibility for the attack one hour and five minutes after it was bought.
Forty years ago, McGlinchey was convicted along with her sister, Dolours Price, for their part in an IRA car bomb attack on London's Old Bailey courts.
One man died of heart attack and more than 200 people were injured in the 1973 bombing.
McGlinchey was released early from prison on licence, but her licence was revoked in May 2011.
She was returned to jail on the direction of the then Northern Ireland Secretary of State Owen Paterson, weeks after the dissident republican rally in Derry.