I would question how a level three could be such a great demon slayer that she became Zariel’s pet dog, rather than just another faceless arrow cushion in the blood war, but we already have wyl and Gale in our camp...
I also wonder how, in the chaos that was the nautiloid’s entrance into hell, she was both able to sneak on board and get an infant frog jabbed into her eye. One would think the mind flayers both lacked the time and had better things to do. Like trying really hard not to get killed.
Yeah, her story and her timeline just don't match up. She saw the Nautilus in Avernus being attacked by demons, and then somehow managed to get aboard and then get put in one of the chambers to get tadpoled, all while the mindflayers, as you say, are fighting for their lives.