After reaching her mare form, she was finally able to date the stallion of her dreams, Big Macintosh. Long story short, Hikari has always had feelings for Mac, some are a safe feeling, I guess due to their relationship and the fact that Big Mac saved her a couple times. Their couple relationship is going well, Hikari lifts up Big Mac’s mood when he is feeling down and Big Mac makes her happy with friendly conversations, lol you get because he only…says…eeyup…funny.
Also when she reaches a certain point of positive emotions Hikari tends to give off a glow a sorts in which can easily be seen during the day.

Big Mac/MlpFim (c) Hasbro and Fausticorn
Hikari/AfterVerse/Art (c) (me)