She's pretty clearly got a bond with the aeons, I reckon. She knows that they were once living people, like her, who chose a similar path by sacrificing their futures to aid the generations to come. The aeons are trapped, only able to touch the real world as manifestations, and then only when a summoner calls them to aid in a fight; although trapped between life and death, they can still be hurt and defeated. Yuna's a very sensitive woman, I'm sure she'd sympathise with that kind of fate.