Biggest supporter.

"My uncle hadn't been single all these years," Gianna spoke carefully, keeping her words in check. "He had a girl in his heart. Not for a year or two, but for an entire decade. And that alone explains how much devoted he must have been to her. No one was able to deter his heart, not even the distance of miles they shared. He had been the only —" 

"...woman he had ever loved in his entire life," Arwen finished it for her, before continuing further. "The only woman who had taught keep the promises and then live it until the end." 

Gianna was dumbfounded for s second. She stared at Arwen, blinking her eyes in confusion. "How do you know?" 

Arwen smiled. "I have known it since always," she said, her expression not even holding a hint of surprise. "He never hid it from me. He told me the very first day I asked him, without even hesitating as if he never had plans to keep me in the dark."