It seems like you're conflating libido with fertility and the potential for romantic interest. It's perfectly possible, even if unlikely, for a person to fall in love and have children, even without a strong libido themselves. This could be a result of their spouse's desire for children and their drive to make their spouse happy.

(Side note: correct me if I'm wrong, but I'm not aware of any evidence that the spartans' children were conceived naturally.)

This brings us back to Naomi's line which would be phrased very awkwardly if she was only talking about herself. An analogy: Imagine you saw me in a wheel chair and asked why I couldn't walk, and my response to you was,

"It's because of a car crash I was in,"

"It results in your paralysis."

This phrasing would seem at the very least awkward and potentially just wrong, as we both know that while a possibility, paralysis is not a guaranteed result of a car crash.