i didn't miss those, but it seemed food was rationed heavily. 1 Burito a day isn't enough, also yeah i saw the gym but even with proper modern diet and workout she would need more than 3 years to go from flashback to her current muscle mass and very probably steroids too.
My head cannon is that she is indeed on roids, but that really isn't a fact since the game never tell you. Also why is no one attacking zarya or other examples in this thread, i feel like it's unfair to just attack people for hating women with muscles just because someone said that abby is kinda unrealistic in the context of the game.
also the problem is not that she has defined muscles actually it's her muscles mass, she actually isn't that defined
i dont think i have seen any character stronger than abby other than those big mini bosses but they come in both genders anyways