I wonder why she's doing her "coming out" there? Previously it seemed as if she tried to remain secretive. And a random high school girl won't even understand what King she's talking about (I'd assume) so what's the point here ... unless Liberta / Komari is nearby, unseen by us?
Nah, this has nothing to do with Liberta being close.
Eri clearly likes the blonde cutie. She wants to have with her a relationship like Liberta with Komari. But for that to work she needs to reveal the truth about herself, who she is and what she does. She must have been waiting a long time for the perfect occasion. When she heard blondie wishing death on everyone, she thought the right time had arrived.
Now we wait for next chapter and we'll see blondie's reaction. Either she will be thrilled and throw herself in Eri's arms (yay!) or she will be horrified and her rejection will break Eri's heart (boo!) but whatever the case it'll make for good dramatic developments.
I mean, she's not wrong...
And that's the author's message, successfully conveyed! >:-D