The criminal hearing to determine responsibility for the deaths had been postponed four times after the owner of the Gympanzee daycare centre, Iman Al Kuwari, failed to show up.
Her appearance in court means she is able to mount a defence against the charges - something which hung in the balance after her last no-show earlier this month.
A court official earlier told Doha News that today's hearing would be the last time Al Kuwari could be tried "amicably", after which she would lose the chance to mount a defence.
The others charged over the mall fire include Al Kuwari's husband, mall management, Civil Defence officials and insurance company representatives.
The relatives of victims were reportedly teary-eyed as the defendants appeared in court for the more than half-hour hearing.
They told Doha News their expectations had been low after the postponements, but progress had been made.
The triplets' father, Martin Weekes, earlier this month expressed his frustration with the delays to the hearing.
"The delay in the legal system is beginning to shed an unfavourable light on the country and the courts."
Three weeks after the fire, Nike released a statement saying it was deeply saddened by the deaths.
An investigation report found the fire was sparked by faulty electrical wiring in a fluorescent light in its store.