In an action scene, short is better, and in a battle, people do not have time to reflect (unless they have magically fast thinking). IRL fight training, there is a strong emphasis on repetition to make your defensive moves "muscle memory" automatic, so you take care of that part subconsciously (as you eventually learn to do when riding a bike, driving a car, typing, even learning to walk). In Kung Fu; they call it your body "becoming" Kung Fu; so your body blocks or ducks a punch the instant you recognize one is thrown, your leg catches a kick the same way; because in practice you've blocked hundreds of kicks. When defense is automatic, your mind has time to think on offense, but again that is just think "punch" and the body throws the punch in good form. Just like I think the word "expert" and my hands type it without further mental attention by me.
In real fights for amateurs, adrenaline and emotion (anger or fear) severely impairs the frontal cortex, the seat of logical thinking. It takes much training to be able to actually think rationally in a fight.
So if you want your girl to have an epiphany, I'd suggest she have that either well before or well after the impulsive move to save somebody else.
For example, when asked by the person she saved why she did it, she can say,
"I have no idea, I just did it. But I was thinking yesterday, I don't want to be a coward anymore, it is ruining my life. So, maybe, that's not who I am anymore. I hope that's not who I am."
"Well, you picked a great time to change it up. Thank you."
Realistically, in a fight (without magical mentalities), only the most experienced and trained fighters have time to think, plan or strategize, and the instant between realizing a trigger is being pulled (which might be done with training) and getting into the path of the bullet is far too short for any kind of deep thinking.
This is one of the reasons we use short, choppy sentences in fight description, and avoid metaphors and allegories; they don't fit well.
Now that doesn't mean "detail" cannot be included, I have fight sequences that in real time might be two or three minutes long, but go on for pages. But it is in the style above; the narrator is describing move-by-move, quick thoughts and realizations about the fight, without much decoration. No deep thinking.
Brittney's right forearm had Angela in chokehold. As Angela tried to pry it loose, Brittney took a half step right to regain leverage. Angela could see Brittney's left foot.
She leaned into the choke to force Brittney to support her weight, and stomped hard on the bridge of the foot with her heel. Brittney yelped and loosened her grip immediately. Angela thought she might have broken a bone. Angela freed her right arm and grabbed Brittney's right pinky, yanking to fold it backward and break it.