Yoko never loved Joe as a person, and this can be proven objectively since she noticed the symptoms of his illness as early as the Hawaii arc in the manga. She was worried, but not enough to stop picking fights with him. In the manga, she even set up the fight with Harimau despite having those suspicions. If she had truly loved Joe, she would have acted differently.

Yoko knew Joe was in bad shape (suffering from brain damage and losing the spark in his eyes). Yet, she still prioritized her role as a promoter, her own entertainment, and Joe's public image as a wild boxer.

This contrasts with Noriko, (who genuinely cared about Joe as a person) and had been begging him to quit boxing for his health since much earlier. Yoko, on the other hand, continued to view Joe more as a concept (the untamable boxer) than as a real, fragile human being broken by the sport.

Yoko liked being part of the boxing world through him, and she found it entertaining to "manage" such a charismatic fighter. Her love was directed toward the superficial figure of the "boxer of the poor" rather than the actual person.

That is why when Yoko finally tries to stop him, Joe doesn't believe her. In the manga, he responds with a joke after her confession, essentially calling her a "cheap whore."

They cut this from the anime because the director, Osamu Dezaki, prefers to be more subtle, using Joe's expressions to show that he detects insincerity in her words. Audiences often miss these facial expressions, whereas the manga is much more direct.

Either way, both the anime and the manga convey that Yoko's love isn't genuine, as she is merely obsessed with his image as a boxer. This is a narrative thread that spans from the Hawaii arc all the way to the end.

Yoko never loved this man