User blog comment:Paul.rea/Teen Wolf News 051816/@comment-27038309-20160520072526/@comment-26879545-20160523120015

"Really? Is that what you're going with? Jennifer didn't kill of them. They sacrificed themselves, you're trying to twist it into something it isn't. Theo murdered Scott, Jennifer didn't kill any of them."

Her actions led to them sacrificing themselves for their parents. They temporarily died. Her actions caused them to die, so she was responsible for their first, temporary deaths. You cannot argue this because it happened in canon. Jennifer Blake was indrectly responsible for the deaths of three main characters; long before Theo came crawling back to Beacon Hills.

"Theo murdered Scott" but Scott also came back, so that's also another temporary death. In terms of "permanent" deaths, no villains have actually killed a main character... well, Void Stiles still did, but that was because the Oni did it for him.