Not so much a reincarnated personality, just a character by the same name that has some similar overlapping origins to preceding"Mother" characters from the show... I may have details wrong here, but the rough jist of PSO2 Meseta these recaps is about right... I think The Mother (Brain) out of Phantasy Star II is a generation of a race of"Earthmen" people, designed to restrain the starsystem's resources such as the reasonably Earth-like Palm, but is finally tainted by Dark Falz/Force. Under her watch, Palm ends up becoming completely destroyed by colliding with a satellite.
At some point, she is tainted by Dark Falz, and it warps her to the point her directive of"preserve the world" makes her think that the best means to do so is wipe out all life in the world so it can't ruin it and drain its sources, and before the beginning of the game, she razes the planet and wipes out most organic life, and wipes out the memories and melts down most CASTs.
She corrupted as well, turning CASTs on her community mad, and must be destroyed to stop her corruption from wiping out everything and spreading. Also, it is not just her fault, but there's a similar satellite-collision incident in PSU's plot - that the colony that the PSU equal of ARKS is inscribed on orbits Parum, also is sabotaged poorly enough that its orbit starts decaying along with the residential sector has to be buy Phantasy Star Online 2 Meseta gleaned from the remainder of the boat, resulting in the rest of the channel crashing to Parum - it does not destroy it, but it wipes out a city, and leaves a huge crater and uninhabitable region around the crash site.