The story's been going on too many parallel lines lately. Characters with less impact are easy to forget since a) it's monthly b) they appear for little time. It makes the story harder to follow.
I think the problem is more that there's no real hook for her. Most of the characters seem to be parodying/subverting romcom cliches like Akina and Ranko doing the love triangle. But Kei seems like a straightforward version of the "love rival who liked the ML from afar but doesn't have a chance" character and, well, we already kind of have that role filled with Ranko except Ranko's actually funny and memorable because the focus is more on her completely half-assed rivalry/friendship with Akina.
I think the other mistake was putting Kikuka into the Manga Club because her and Ririku's thing seemed to be leaning into/parodying yuribait friendships but now her chapters are just about the Manga Club stuff which is an obvious pisstake on romance cliches, manga production, shipping and fandom. And those chapters are some of the funniest but again we already have Tasaki and Tsukishima filling that role and the side effect is that it's made Ririku sidelined and aimless.