I sure hope she's been drinking enough water to replace all the fluids she's losing, like goddamn man.
Hentai artists scoff at your "laws of physics" and "conservation of matter" and "refractory period". She(?) can cum more cum than her whole body weight using the same mechanics as Bugs Bunny can pull a hammer larger than himself from hammerspace, so long as the artist/commisioner likes that stuff.