Lexi grew up on Omega. Her mother was a dancer and her father was a turian bouncer. She spent a lot of time patching up her father's injuries and discovered she was good at it, which led her parents to spend every credit they had to get her the education she needed to become a doctor. She lost both of them in a turf war at some point before she joined the Andromeda Initiative.
Lexi's thesis on krogan virility and aggression in particular allowed her admittance into the Initiative. She also struck up a friendship with Dr. Harry Carlyle, whom she met at a medical convention on the Citadel. When Lexi and Harry joined the Initiative, he insisted that she come with him on the human ark Hyperion, which she was eligible for due to her knowledge of human anatomy.
Mass Effect: Andromeda
After the planetside mission on Habitat 7, Lexi takes Dr. Carlyle's place as Pathfinder Ryder's personal physician. She always wanted a field posting and thought she'd only be waking up colonists, but the presence of hostile aliens and environments moved things a bit too fast to her liking. Since she's a specialist in alien biology, she finds that there are plenty of opportunities to dissect kett specimens in tagging along with the Tempest crew rather than back at the Hyperion.
Ryder can flirt with Lexi, but the doctor explains that the human just isn't her type. She's averse to forming romantic entanglements with her patients as she needs to look at them objectively and without distractions.
After escaping the Archon's flagship, Lexi voiced her disapproval with SAM killing and resuscitating the Pathfinder.
While Ryder is in the Paradise on Elaaden, they can assist Lexi in deducing the stasis pods on the Arks led to chemical imbalances in the brains of some of the passengers, leading to the violent behavior of the Nexus Exiles who would go on to plague the Heleus Cluster as scavengers and outlaws.
Once the Tempest takes flight again after Landing Day celebrations in Port Meridian, Lexi pesters Ryder again with more medical exams if the human visits the medbay, in light of the significant physical and mental stresses the Pathfinder experienced recently. If Ryder sarcastically insinuates a headache coming up, Lexi no longer rises to the bait owing to her familiarity with the human. If Ryder claims normalcy, the doctor then claims the human no longer was ever since Habitat 7. While Ryder grudgingly complies with her prodding, Lexi announces that she has been offered a posting in the Nexus by Professor Herik. Her research on kett anatomy has proven to be useful for the militia.
Regardless of Ryder's responses, Lexi has already turned the transfer down. If Ryder takes the news flippantly, Lexi snarks back that no other doctor would want to take on the Pathfinder. If Ryder tacitly allows her to go, Lexi reasons she does her best work out in the field, and she muses someone needs to look after the Pathfinder. If Ryder expresses gratitude, Lexi concurs they both lucked out being in the Tempest at the same time. If her lifesaving skills are praised, Lexi highlights the two times Ryder "died" under her watch - technically three times, but she doesn't count the first one as Dr. Carlyle was the attending physician then.
First message received after speaking with Lexi on the Tempest.
Received after the conversation including Jaal about exaltation, if you tell him that exaltation is permanent.
Received after the conversation including Jaal about exaltation, if you say that there could be hope to reverse exaltation.
Received after Lexi T'Perro: Bottom of a Bottle.