There is an email from Dr. Capria and Dr. Orlov that says TYM sent Daria (and other memory implant patients) to Dr. Orlov. Since Dr. Orlov is the only person known to install TITAN Shield augs in people (Jensen and the Gold Mask Mercenaries), it's reasonable to assume that Dr. Orlov installed the Titan Aug in Daria as part of his experiments. Why he did this, I do not know, maybe as a test before he put Titan augs in Jensen and the Gold Masks, or to make Daria's Harvester personality a more effective killer, I can only speculate.
Update: I reread the pocket secretary you get off of Daria. Dr. Capria does call her "Orlov's child, not mine." And it states that the "tools" Daria uses cannot be reconciled with The Harvester's ideals, implying that Daria's Harvester personality did indeed use her augments to kill more effeciently. I think that this info also implies that it was Orlov's tinkering with Daria's implant that caused The Harvester's personality to take over.