After you defeat the Viola A.I. that took over Ken's frame, you will receive this trophy:
Next, you will have to help Ken get out of the building. There will be a lot of enemies spawning above you (and these guys can be annoying) and a lot of red-hot magma below you. Grab Ardjet (Ken's frame) and get her nice and close to all that searing goodness. She will complain, and lose health, but keep her down there for a few seconds. It is also best to disengage the lock-on feature so the baddies can't restrict your movements.
I had her down in the lake of fire for 15 to 30 seconds. Afterwards, just take her straight up. There will be a cutscene where her and Dingo will talk, and then she jumps in your cockpit. The trophy will pop shortly after she enters.
Questions, corrections, or justifications for neg votes in the comments field below.