I think he did deadass like her before but respected her and his sister perhaps. Maybe more his sister. Then the arrow just amplified what both were feeling. His love, hers resentment. It must have felt pretty poopy to go so many years loving someone only to not be able to have it. Especially if that someone gave you glimpses of hope.
Like I think that’ll be the “plot” twist. How neither was actually effected to much by the arrows it just amplified their emotions. He is the god of truth etc. I think he’s being honest with her.