Greta Reynolds is the wife of Davin Reynolds and a colonist of Zhu's Hope on Feros. She guards the entrance to the colony and protects the colonists from any potential threats.
Like all of the other colonists, Greta Reynolds has fallen victim to the mind control capabilities of the Thorian creature. She waits with Ledra and some inactive Thorian Creepers behind heavy covers on a chokepoint walkway in anticipation of Shepard's return. Shepard has the choice to either use the Anti-Thorian gas grenade to save Greta and the other colonists or slaughter them outright.
If Greta survived the Thorian's destruction, she's grateful to Shepard for her freedom. The Thorian forced her to think what it wanted, and she felt its death during Shepard's assault. She's glad to have another chance at life, which is what she and her husband wanted all along. However, if she lived while Davin died, she will be absent from Zhu's Hope in the aftermath. If too many colonists died and her husband's still alive, she plans to get out with him and move back to Earth: the sooner Feros is a memory behind them, the better.