I'm finally watching last week's episode, and it's quite horrible to see how Yvette is giving Derek the cold shoulder. Currently at David's reading and it's incredibly obvious how little she's spoken to Derek, as well as her defensive/bored stance and badgering him for names and dates... There's none of the old camaraderie of the olden days; it's as if she barely tolerates him.
I hadn't noticed it before now, but in light of the recent information, it's evident there's some animosity between them.
(That being said, she seems to be in a bad mood as it is, but she's spoken more to David during the proceedings than Derek.)
A sad day indeed.
*reinstates old D/Y icon to remind us of better times*