Much like BlackGold (and unlike Cold & Dark and BlackIce), the loneliness that Pitch would bond with would be far more internal than external. Much like Jack, Rapunzel and Elsa, Anna has felt a great deal of isolation in her childhood, both being locked away in her castle, confused about her only sister and best friend shutting her out. But where as Elsa or Jack has allowed this despair and lonliness consume their actions into inaction and rebellion, Anna has simply allowed her isolation to germinate into a blissful ignorance, latching on to the smallest bit of attention given to her (like from what she had with Hans) and ignoring the obvious.
Pitch may find the princess's optimistic and extroverted tendencies annoying, even insulting, and may try to extinguish the light within her with his fear. As she grows older, he may learn to tolerate, even admire, her love of whimsy and wonder, and accompany her in different endeavors. He might even compare her head-on tenacity to his daughter Emily Jane. Much like she would with Jack Frost in Janna, she may see him as some kind of imaginary friend or "fairy godfather", coming to consolidate, lecture and give advice to her as a father would.