First of all, when a Pokemon is traded its happiness will reset the the default(70). So you will have to start over again.
Second, you must remember that Pokemon Amie does not affect happiness, only affection. Affection has no effect on Golbat's evolution. It only affects Eevee's evolution, evolving it into Sylveon.
>In Generation VI, friendship is not to be confused with Pokémon-Amie's affection. Affection is an entirely separate stat having no bearing on friendship, and no actions taken in Pokémon-Amie will affect friendship in any way.
This chart shows how to gain/lose happiness "points" with a Pokemon:
>Friendship is set when a Pokémon is brought under a Trainer's control; i.e., it has a value of 70 when a Pokémon is captured from the wild, and reset to 70 when a Pokémon is traded from another game.
So you would want to obviously do one of the first two things whenever possible.
Hope I helped.