My Fair Lady. Even with “I’ve Grown Accustomed to Her Face” – the closest Higgins comes – he doesn’t say anything about loving her.
His Girl Friday. At most, they refer to their earlier marriage, but don’t express love now.
An example of a movie mentioned here that I think is only about friendship is 84 Charing Cross Road. Frank was married. Helene apparently had lovers. There’s no reason to think that they desired, even unconsciously, to be in a romantic relationship. The film is about the relationship between two people that starts out to be just about business and ends by being about friendship.