Probably not too likely this was done last night, since she's the chair. Could be someone has a night action and picked DK, she's a logical choice, more likely though someone has a day action and targeted her as the chair. Now it's fairly unlikely they would have used it till voting was in full swing, so it's not too likely it was one of the other voters, or one of the inactive players. Of course, this could be a deliberate effort by Yuna to have set up a situation where she could prove she was a vote-blocker but that makes little sense, so let's just look at the non-voters for Yuna, minus Hobo, Yunalesca and Amys.

Artsapat
BlackAdder
Kronin al'Sulc
Kylia Skydancer
Napoleon62
White Flame of Tar Valon

So one of these players probably has vote negation. I'd like to hear from them, confirming or denying involvement