Briah = a supermagicpower determined by one's deepest desire. The desire is the statement, the Briah is the power derived from that statement. Plus, Abnormalities are abilities derived from the user's own personality and ability, and her Abnormality lets her copy those.
Grows stronger the more enemies she faces is simply a way of saying that she would most definitely stomp the LDO apart from Reinhard. For one thing, none of them are even close to 5-C, which in this state is her absolute minimum. For another, she easily has the hax to deal with them. And its one of her 100 trample skills, which are not on the VS battle page, but the Medaka Box wiki.
As for Mid-Gody regen, yes effectively. She can bring anything erased, even conceptually, back into existence. And All Fiction has turned people's deaths into fiction before. Seeing as Medaka Box hasn't shown any evidence of souls/afterlife (for them to use All Fiction from) that I know of, we can assume either two posibilities. Either All Fiction can be used regardless of the user's state of being, or its use can be linked to a "trigger event", such as the user's death/erasure. Either way, Medaka can return herself from erasure. So if Reinhard smacks her with the spear, either she erases that event with All Fiction, or she un-erases herself with Non Fiction.
