User blog comment:TheMangaGoddess/Why Does Snow Love Bigby?/@comment-86.137.51.16-20170127212929

"It's explained in the comics" is all i can really say.

Long story short, it dawns on her slowly as she raises his cubs, that no matter her repulsion to her ex-husband, she is still that girl who wants a charming prince to sweep her off her feet, and that through everything Bigby's always been there for her.

And as she raises his cubs, she begins to understand more about his nature as a Wolf and as son of the North Wind. It's a slow and gradual understanding. She realizes she was pretty ignorant of his perspective on the world and falls for him through understanding.