Miranda Lawson may be the so-called perfect human, but she’ll assure you that she’s far from it. She excels at anything she does, and never leaves a job half-assed - she completes it to its utmost peak.
She was “crafted” by her egoistical father to be as perfect as humanly possible. Yet, he was dissatisfied and kept pushing Miranda past her limits; he always wanted more than she could give. He even went to the extent of creating another daughter, one who would replace Miranda. She had enough, however, and ran away from her privileged lifestyle. She found protection in Cerberus, and quickly got into the good graces of the Illusive Man and is still to this day one of the few people in the entire galaxy who’s had direct contact with him.
Miranda quickly found a home in Cerberus, appreciating the opportunity to work with people who were as intelligent as her and who appreciated her abilities. When Commander Shepard’s body was recovered, she was placed in charge of rehabilitating her back to the exact person as she used to be. From there, she was placed as Shepard’s second-in-command during her mission to take down the Collectors. The pair often butted heads over ideals, but when it came down to it, Miranda had her back. She began to warm up to Shepard after she helped secure her twin sister, Oriana, and her family from her father. She now, and will forever, hold a large debt to the Commander and respects her immensely despite the differences.
When Shepard decided to blow up the Collector base, Miranda finally saw the Illusive Man’s true intentions and left Cerberus. She stuck around with Shepard until Cerberus took back the Normandy SR-2, in large part from the IM’s rage. Since then, the Illusive Man essentially begged for Miranda to come back to Cerberus - that he needed her on his side to help the Reapers. While she agreed, she went off and did her own thing. She is now a private investigator under the name “Amanda Solheim”, and gives the Illusive Man false reports on her search for Shepard and assassinating her old crew.
Miranda knows the fight with the Reapers is just getting started, and if Shepard ever asks her to join with her again to defeat the imminent threat, she would accept in a heartbeat. Nothing would please her more than to see the Reapers and Cerberus fall.