Responses
Well, in the Original novel, the reason why Soleia was so hell bent on marrying Erudian is because she wanted a child that will inherit his deivine power and her black magic..But the experiment failed and Deckard was born with only black magic abilities and no Divine power.
If Yenni and Erudian get married, Deckard might actually inherit his father's divine power this time and therefore won't be able to practice black magic. (since the experiment's failure suggests that both opposing powers cannot coexist in the same person)

What if she succeeds in marrying him but then she is the one who gives birth to edckard!! And soleia still trains him