Wow, this makes the manga and Ayako and Asukas development so much better! Because this means Ayako also has had thoughts subconsciously before Asuka confesses. Soul mates?!
I was actually thinking the opposite, in that Asuka's body language was really obvious, yet it took Ayako until the middle of the next day (plus a hint from an unsuspecting co-worker) to put her finger on what it was. It suggests it was totally outside her thoughts (if she had feelings of her own, she probably would have jumped to a conclusion about Asuka more quickly). That's why I was wondering how obvious the delicious/oishisou ref was - ie if it was something an "innocent" mind would catch.
I have a feelng Alexrain is on the right track ( https://dynasty-scans.com/forum/posts/521809 ), I'm not sure I think it has been as long as the whole two years, but Ayako acts so naive/inexperienced that it seems like this may be her first time falling in love. Even as she tells herself off for acting like Asuka's [jealous] partner, until this last chapter it doesn't occur to her she is acting that way because she is feeling that way. Interesting implications for her relationship with Asuka's father, and what Ayako and Akira may have to feel guilty about. I smell a flashback coming.
Building on that theory also suggests a different angle on the kissing thing - it has been stated Ayako has a lot of experience with people having crushes on her, yet it seems her legendary coldness always kept them at bay. She never reacted to their feelings, and that put people off. In addition to her tendency to coddle Asuka, her past experience may have led her to expect that people would just lose interest if she humored them (a couple of fatal flaws - Asuka is really persistent, and Ayako does react to her).