Yami didn't saw Hikari, it's an After-the-fact naration
To me, the last part sounds more like she’s narrating it afterward, not actually saying she saw Hikari there.
Yeah maybe you guys are right but idk feels like the narration was still from her pov but yeah idk lol.
But if it does turn out she saw Hikari, feels like it would be important to know whether she saw it BEFORE or AFTER the kiss lol.
Yami still sucks, but if she saw her only after the kiss, it could at least lower her level of suckness a little bit lol
EDIT: You know what, i think you guys are right and i am wrong.
I just read the manga chapter again and I think last panel of the manga confirm Yami cant see Hikari hiding behind the door so i think its confirmed Yami didnt saw Hikari.