She wants to make fifth-circle and Teleport herself the fuck out of Cheliax and live the rest of her life answerable to nobody, is what she actually wants. And then at the end of that, go to the gardens of Erecura forever, or go to Abaddon briefly.
Keltham may have neglected to explain the difference between aromantic and asexual, and Taldane certainly isn't helping out with words for such things. But even so, Asmodia knows, she is not just sexually unattracted to Keltham. She does not dislike him, and for certain if she had to be with one man out of Cheliax she would choose him; but there is nothing about the thought of living in his household that appeals, compared to the thought of just walking away from everything.