>Stream like nothing happened
Will probably bring some harassment her way for awhile, but it'd die down in a few months.
>Put your graduation request, stream like nothing happened and apologize when you go out in a few months
Will probably bring some harassment her way for awhile, but it'd die down in a few months. By the time she gets to make an apology/excuse the drama and emotions would have down died and everyone would be ready to move on. A tepid apology just enough to shift the blame from her would be enough for her to go on. Her radioactive period would have either passed during her months in Niji or it'd be near the end.
>Immediate graduation / termination, give excuse and move on
Would give her a drama buff and might work to her benefit if she can ride the wave, but it's a bit risky.
>Be allowed to apologize by Nijisanji, then return to streaming (doesn't matter if she graudates later or not)
Harassment period is heavily reduced.
>She was planning to move on from streaming anyway and just doesn't get back
Nothing to discuss here.
In either case I don't think you'll get some explosive or dramatic event surrounding her. She still has her audience that'll follow her outside of Niji, or continue to watch her inside (Enna has lost ~30% of her viewership, I assume it'd be a bit higher for Elira, but nothing terminal). After the drama dies down you'll see the most boring outcome possible - everything returns to normal. The more deciding factor for her future growth will be whatever Nijisanji can recover it's brand to attract new people, fold into JP and other things that are outside her control, at least as long as she's in Nijisanji.