Not sure why you would read that as jealousy or loneliness, even the recipe page seems to directly state that Sachi is both surprised but mostly proud how far Ayari has become. Well, I suppose these things are not entirely mutually exclusive.
As long as I can remember, anyway. It's on the "there's two girls who like doing things together, so they might be gay?" end of the subtext spectrum rather than intentional subtext, to be fair.