In an official AMC interview, the actress praised showrunner Frank Darabont for widening the age gap between Andrea and her sister Amy (Emma Bell).
"Andrea is a little bit different than [in] the comic book," she said. "I think it was a very smart decision that Frank made, having Andrea be 12 years older than Amy, as opposed to 2. It's a much deeper, richer...relationship."
Holden also described her part on the zombie drama as "a real gift" for an actor.
"[Andrea is] trying to protect her sister, but she's also trying to repair and rebuild this relationship in a world that has no hope," she said. "Those are pretty powerful things to play in a six-episode arc on television."
Emma Bell previously claimed that the zombie drama would focus on the "emotional connection" between the two sisters.
The Walking Dead continues on Fridays at 10pm on FX in the UK, and on Sundays at 10/9c on AMC in the US.