The premise of this manga wouldn't work if we found out about her sex life or, God forbid, the characters would just communicate like normal people. She's supposed to be Schrödinger's slut.
Dunno, it truly depends on what story author wants to tell and how.
If the intention was to make a story focused on themes of sexuality, with a promiscuous FMC, there's various examples out there (Meguro, Our Dating Story, etc) though on this stories the girls become focused on the male protagonist the moment they meet him.
If his intention was having an FMC that remains promiscuous, at least for a while, there's "Daredemo Dakeru Kimi ga Suki", which is about a guy that gets a crush on a girl who is a self-proclaimed slut. Theres no tricks or fakeouts there, she is sleeping with other people, MC discover it from the very first chapter, and the whole series (based on a hentai doujin but now with an actual regular manga) its about MC trying to get closer to her without ending stuck as just another of her sex friends, as (at least initially) she makes it clear she isnt interesting in dating anyone, but its open to have sex with him and others.I
In any case it just feels silly to have this manga wanting to constantly confuse the readers about the girl being or not promiscuous. Its not something readers will find entertaining if it drags too much.