Here, I'm going to detail how ME!Erika differs from Sage!Erika (hereafter referred to as simply "Original"), though there will be a few minute similarities here and there.
Preliminary Notes
Erika Dumonte is one of 20-some odd characters from my own universe, a little something-something I like to call
Emerald City, named after a fictional island city out in the middle of the Pacific Ocean. As one may surmise by the last sentence, it takes place here on here on Earth, set in the late 2060s.
Basic History
ME - Earthborn. Look up the Mass Effect wiki for exact details.
Original - American, specifically from NYC. The younger of two daughters, Erika was adopted into another family after her parents thought they couldn't handle raising two girls, especially with the significant age gap between the two (Sonja, Erika's sister, is 8 years older).
Unfortunately, Erika's adoptive parents were also preoccupied with their own prodigious daughter. Desperate for attention, she tried numerous hobbies including playing the violin and the flute, but could never reach the level of aptitude of her adoptive sister. Finally, after watching a few classic martial arts films, Erika found her calling (specifically learning Taekkyon). However, this only increased attention gap between Erika and her foster parents since they felt "a lady had no business willfully engaging in fisticuffs", thus leaving Erika to grow up alone and flustered.
Erika's school life was a chaotic one. Her teachers would often deem her a menace for getting into numerous fights; it quickly became a running gag that people would place bets on how long it took before an ambulance arrived, for it seldom became an issue as to whether or not Erika would win, but rather just how bad she curb-stomped her opponent. She was finally expelled and place into an international all-girl boarding school when a fight resulted in a student having a concussion, a broken jaw, and 4 missing teeth (for the record, she basically embarrassed him in front of his friends, and he didn't take lightly to that).
Erika then stayed low-key and eventually caught word that her birth-sister Sonja had just finished a tour with the Marines and was well on her way to obtaining a PhD in bio-genetics. Struck by admiration and inspiration, Erika herself enlisted in the Marines right out of high-school.
Military Career
ME - Ruthless, Active Duty (as the series is still going on

)
Original - While originally wanting to go into medicine and jump-start her own path to obtaining a PhD like Sonja, Erika - and various training instructors - noticed she had an impressive knack as a rifleman, she being one of only a handful of Marines to achieve a perfect score on the Rifle Proficiency Examination. She was recruited into sniper school shortly thereafter, and achieved an impressive score in that examination as well. As such, she was deployed to a relatively new base in China as the Chinese government was on the verge of collapse and civil war was just beyond the horizon...
It was there that Erika met one Claire Snowdrop, an orphan hailing from Vancouver. Claire was very similar to Erika; they both were adopted (though Claire's an only child), they both were very accomplished martial artists, and they both grew up violent and resentful of others. And they both were very proficient riflemen. Much to Erika's surprise, the two hit it off quickly and those memories of loneliness and anger quickly faded into the recesses of both girls' minds.
Things took a turn for the worst about a year later, when the military base was hit by rebels in a late night sneak attack and prompting a violent skirmish lasting approximately 15 days. Erika showed her courage - or recklessness, your call - when she deliberately disobeyed orders and manually disarmed an enemy squad, receiving a gunshot wound that narrowly missed heart by just 2 inches.
What could best be called the lowest point in Erika's military life was when she volunteered to search for a scout party that failed to report back at the appointed time. After some time looking, she eventually found what was left of the scout party: Claire, mortally wounded and rapidly losing blood. Erika did her best to treat the wound, and decided to stay with Claire until help arrived. Unfortunately, the damage was worse than Erika initially assumed and Claire eventually passed away in Erika's arms a few hours later.
Eventually the rebellion was quashed, and order had been restored to the Chinese government. After Claire's funeral, Erika got a tattoo of a snowdrop flower over the scar created by the bullet wound in her chest, a reminder of the one true friend she had - and lost.
Erika eventually moved to Japan and finished her tour with Marines there. She now lives in Emerald City with her sister Sonja, living life quietly and still trying to get that PhD in medicine.
Disposition
ME - Paragon, with a bit of Renegade for flavoring (to show that she's a good girl, if vulgar and impatient)
Original - in terms of alignment, Erika is probably best described as a Chaotic Good. Remember, her foster parents cared little for her other than the basic necessities, and she had no friends growing up. This didn't make her a delinquent though, just... resentful of others in a "fuck the world" kind of sense. Besides, she wants to be a doctor just like her sister one day. ^__^