Zara Kelly (35) scratched and punched the doorwoman as she lay on the ground being kicked in the ribcage by a male accomplice, a court heard.
Judge Bryan Smyth adjourned the case at Dublin District Court for victim impact evidence.
He warned Kelly she could face jail over the attack outside a city centre clothes shop.
Kelly, from Ballyogan Avenue, Carrickmines, pleaded guilty to assaulting the woman, causing her harm.
The incident happened at Guineys' shop on Talbot Street on September 1 last year, when it was reported to gardaí at 3.45pm that a security woman was being assaulted.
The victim had stopped a man and woman on suspicion of theft when the pair became aggressive, getting into a physical dispute with her that spilled out on to the street.
The security woman alleged the man kicked her a number of times in the ribcage while she was on the ground and Kelly "scratched and punched" her during the attack.
The assailants had fled the scene but were located and arrested. Kelly denied the allegations during interview but there were independent witnesses, a garda sergeant said.
The security woman suffered cuts to the face and bruising to her ribs.
Kelly had previous public order convictions.
The accused was "doing extremely well at the moment, having completed a number of rehabilitative efforts", her lawyer said.
What happened was "not very nice" and the accused "may be facing a custodial sentence", the judge said, reading a medical report. He said there should be "some generous compensation".
A co-accused, Stuart Blair (28) of Monksfield Lawn, Clondalkin, has pleaded not guilty to the same offence and his case will be heard next June.