The investigation into Tongia's death is continuing, police said.
The woman is now the fifth person charged in relation to the homicide.
A 19-year-old man was charged with being an accessory to murder three days ago.
Two women have been charged with murdering Tongia, a 35-year-old and a 24-year-old.
A 20-year-old woman, who is accused of being an accessory to Tongia's murder on December 20, grinned and mouthed words to her supporters as she stood in the dock at the Wellington District Court on January 21.
Court documents allege the 20-year-old "actively suppressed evidence" by hiding a firearm at an associate's property to help someone avoid conviction.
Police revealed in January they had found a firearm during a search in Wilton that they believed was linked to Tongia's death.
It is being forensically analysed.
Police said they are also looking into whether the weapon is linked to other offending across the district.
In late January, Wellington field crime manager, Detective Inspector Darrell Harpur foreshadowed that more arrests would be coming after police charged the 24-year-old woman.
"This is the third arrest we have made in relation to the death of Mr Tongia, and while the primary offenders have now been charged, I am confident it won't be the last," he said.
Last month, police extended their sympathies to Tongia's loved ones.
"I want to acknowledge the investigation team who worked tirelessly on this very complex case, and commend them on their professionalism and dedication to holding those involved to account. They worked long hours and took valuable time away from family throughout the holiday period to ensure justice was done for Rau Tongia."