What would the White Court of Vampires have to do with Lea and Justin? Yes, Lord Raith murdered Harry's mother, but I don't see any evidence that he had anything to do with either Lea or Justin.
I should have explained. It's manipulation on a scale that someone like Lara Raith could admire, though Lara or any of the Raiths would have used a different method to attain it.
Lea makes a deal with Margarite LeFay to protect Harry, then while still fulfilling her given word, either allows Harry's father to be murdered or does it herself as part of a deal with Justin DuMorne. DuMorne thinks he has won a great prize but Lea has simply offloaded the drudge work of teaching Harry basic magic skills until she can find a way to dispose of Justin. A break between Justin and Harry (Did Lea have anything to do with that? Meaning, did she have another deal with whoever summoned HWWB?) allows Lea to get Harry to remove Justin for her and to top everything off, it allows Lea to make a binding deal with a young, desperate and naïve, starborn wizard Harry.
P.S. New topic on the same character. Thinking back to the dénouement of the Battle of Chicken Pizza in Changes, Ebenezer approaches Harry and Lea and asks her to leave so he can discus "family business" with Harry. Ebenezer knew who Lea was and he knew that she knew about Eb and Harry's familial relationship.
It is one thing for Ebenezer to recognize The Leanansidhe; Lea is a very powerful figure in the Winter Court and Ebenezer has been around long enough to have had some experience with the fae, but as was pointed out in Battle Ground, Eb doesn't believe in casually dropping any information about anything, especially family. Even if Eb guessed that Lea knew that Eb was Harry's grandfather, he still wouldn't have mentioned it, he might have said something like "White Council business" instead.
What I want to know is, how did Ebenezer know that Lea knew? Margaret LeFay was on the run and probably realized that her time was running out when she made the deal with Lea to protect Harry. Ebenezer wasn't there. Ebenezer didn't visit Harry in the orphanage, Lea did. Even if Harry told Eb about the deal he had struck with Lea to defeat Justin; after the White Council put Harry under the Doom of Damocles and under Eb's guidance, Ebenezer wouldn't have known how much Lea knew about Harry's family.
Did Ebenezer make his own deal with Lea? I'm not speculating what such a deal might have involved, but those two know each other and not just by reputation. It suggests something more is going on here and perhaps something important.