Losing the battle to her alts and their hangers-on is moderately obnoxious. Still... That's a clever group. She'll have to remember them and their tricks.
The combined forces of everyone whose souls she stole - now resurrected by the alt who shares her face - tear her body apart. Inconvenient.
Acererak drifts, for a while, and then -
Her body reforms, of course.
(Did they really think killing a lich who could challenge gods would be so simple?)
She leans against her phylactery for a while, as her body finishes knitting itself together. She then renews the protections on it, opens a portal...
Staying in her demiplane would be boring, but returning to her usual stomping grounds isn't smart, right now - so a new world it is. Hopefully one with resources she can exploit.
Acererak steps through, stretching her neck, and looks around at where she's landed.