Quoted By:
>take a cosy stroll through Luminose City late in the evening with only my Gardevoir (and some eggs) in my party
>affection in Amie is at 4 hearts
>decide to end my session in style by sleeping in the grand hotel
>check in, rest, check out
>walk barely ten steps
>in the bottom screen where the Amie room is displayed, I get a message that Gardevoir's bond with me has deepened
>at 5 hearts without me having interacting with it in Amie
So in response to the OP: yes, apparently
After this I decided to go full waifufag, and have since beaten the Elite Four a second time using only my Gardevoir. No regrets.