Indeed, this second heart depends on past choices. If you talk about personality, you will earn both hearts if you share her nature—that is, being neutral (neither overly compassionate nor overly ruthless)—and tell the truth.
However, if you choose to talk about her appearance, you will earn the second heart if you say you have a soft spot for redheads and had told Kayane the previous day that you prefer redheads.
In any case, you can always get at least one of the two hearts as long as you tell the truth.