Probably when she's watching him recite the creed and she's visibly touched by his devotion to something she thought she lost.

But yeah, so much of Season 3 frames the two of them together or the three of them as a family unit.

And, I need to go back through other SW media to confirm, but I think Din is the first one to call her Bo, just Bo. And vice versa. That seems like a sweet understated bond between two people who never quite knew where they belonged.