Maera Elizabeth Todd, 39, appeared in the Christchurch District Court on Tuesday alongside Shantai Lawson, 38. Both women were charged with aggravated robbery, but only Todd was charged with assault.
Todd is accused of robbing a phone, wallet and other contents from the couple's home.
"Such an attack on elderly, vulnerable members of our community will not be tolerated," Detective Senior Sergeant Greg Cottam said.
Alongside Monday’s robbery and assault charge, Todd has a kidnapping and robbery charge in Hastings from July 28.
Police said in a statement that a member of the public notified them immediately after noticing a disturbance late on Monday afternoon.
The two victims were taken to hospital for a check-up. They were "shaken but not seriously injured", according to police.
Both women were denied applications for bail and remanded in custody until their next appearance in Christchurch on August 27.