Well actually this all happens in the span between Malcom losing his room and after Malcom stays on Team Rocket's blimp. Damian meets up with two other Gardevoir on the island, Chrys who belongs to Ace and Rose who belongs to Vivian. At first he wasn't exactly happy with their personalities, but somehow Rose started to grow on him-especially in a romantic way
This is just a progression of how they got closer. At some point though Guice ends up attacking the group, and his zoroark injures Rose, badly D: Damian felt guilty about it, but after a bit of talking, Rose assured him it was no one's fault <:3Oh btw. Damian and Rose (the two gardevoir) are BOTH male. Chrys however (the gardevoir with the Team Rocket arm bands) is female.
Pokemon (c) Nintendo