Dahlia and King Ronald have been acquainted ever since Ivan and his siblings were little. King Vince, Ivan's father, the former king was always busy. He didn't have time for anyone not even his children.
Dahlia was chosen to be King Vince's Luna, but it turns out his actual mate was a human girl. Because he was royalty and in order for him to carry out the strong royal blood line, King Vince was stopped from marrying his actual mate and instead arranged to be with Dahlia.
Dahlia loved King Vince, in fact she gave her all in the relationship, but the feeling wasn't mutual. King Vince was in love with his human mate. Even when Dahlia was pregnant and bore him a son, Ivan, hoping her affection for her would change, it still didn't. She was his rejected mate after all.