The Arkanians have mastered the secrets of biogenetics. It is the source of their pride, their arrogance, it is their heritage.
Of course, so does too Rebecca. Hailing from a long line of scientists, Rebecca Allocer has been quite always been a modest one, though for Arkanian standards.
She lets her skills talk for her, and that's where her Arkanian arrogance shines through, so when she joined the Witches of Dathomir,she has but one promise,
"As long as I am here, none of you shall die."
...
So does a promise easily crumble at the face of significant formidable might. The machinations of the Nightsisters have been foiled, and they find General Grievous knocking on their doors as a retaliation. Rebecca watch as the enemy forces annihilated the sisterhood in which she grew familial bonds with. Her knowledge meant nothing, her skills didn't help, and her Arkanian arrogance crumbled.
And so, she ran.
Run, run, run, as far away as she can.
Hide from the bounty hunters.
Survive on harsh environments.
Eat scrap to scraps.
This kind of living, along with the regrets she carries, took a toll on Rebecca's sanity.
Never again.
Next time, she'll take care of everybody better. Next time, she'll fight back. Next time, she'll be more reliable. Next time, she won't run away.
These thoughts swirl in her head as she tries to survive the day to day, which turn into obsessions. It is what kept her going when she doesn't have water, it is what nourished her when she doesn't have food, it is what gave her warmth on the frigid nights.
Next time, nobody will die in her watch.

...

On the medical bay of the rebel's base, one could find a beautiful physician named Dorothy Willow. She is known as a kind and caring doctor, who provides the top-of-the-line treatment the rebellion has to offer. Her care might take long, but rest assured that it is just her thoroughness and dedication to treat a patient. Looking at her, one might think somebody like her couldn't even lift a sword, but those who have witnessed her in the battlefield might beg to differ. Her dexterity with her hands translates just as well in combat, making her a menace for the Empire's forces and a reassuring presence for the rebels. Witnessing her surgical precision applied in battle had earned her the nickname of "Doctor Killgood."