Nakyah Barnes-Nelson, 20, was taken in custody late Thursday. She is a resident of the building, police say.
Barnes-Nelson is charged with two counts of arson and related offenses.
Police tell Action News that the suspect, in a fit of anger, doused a male companion's belongings with perfume and set them on fire on a wooden balcony.
The flames spread from there.
"The agency still has one person of interest we would like to speak with regarding the fire," the Camden County Police Department said Friday.
That person of interest was not identified.
Firefighters responded to the Myrtle Place Apartments on the 4000 block of Myrtle Avenue around 5 a.m. Sunday.
Arriving crews found the two-story apartment building engulfed in flames.
Arson/K9 Unit investigating 3-alarm South Jersey apartment fire
As the roof collapsed, crews upgraded the call to three alarms.
"(Once inside, firefighters) were then able to get to the other units, go in other apartments, make sure everybody got out. So that's a blessing in the course of this tragedy," said Camden Fire Department Chief Michael Harper.
Camden apartment fire being investigated as suspicious, sources say
At least nine families were left without a home. The Red Cross provided families with a temporary place to stay as well as food.
"I opened the door, I see smoke. I ran inside and got my mom out, my brother, started screaming and trying to get everybody out of the building, you know?" resident Nilsa Santiago said.
Santiago said she felt fortunate all of the residents made it out alive.
"That's what matters, the lives. Everything else is material. My mom is OK and everyone else. We didn't lose lives," Santiago said.