I just only now realized that Okuu (which is her nickname) can also mean "to eat" (御食う), which is what she basically does to Yatagarasu (depicted as an orb) to become her present self.
The screenshot shows eplus, which is the ticketing service used by (basically) all BanG Dream! concerts, specifically the application history page (see also asset #41453562). However, the e-mail shown in the anime somewhat resembles pia, another ticketing service (used by Girls Band Cry concerts actually), as can be seen in asset #41453500. It's obviously far from a perfect match, but at least there's some similarities, unlike the eplus lottery result email (asset #41453503).
Both pia and eplus have the benefit of not being l-tike, which I'm pretty sure is a tool of psychological warfare based on how bad it is to use.