If she was actively choosing to die, the show didn't set up her actively choosing to die very well this season. Like when Buffy jumps off the tower in "The Gift," it's been set up all season that A) she'll do anything for Dawn, and B) that she doesn't want to live in this world anymore. So it makes so much sense. With Elena, they haven't laid that foundation in this half of the season.

That means Bonnie KILLED Tyler. I'm very pissed off at that

I don't know about that. It was a contingency plan for if Alaric got to Klaus--if that happened, Tyler was going to die and there was nothing they could do about it, so she decided to save Klaus (to what purpose, we'll see, I guess) by putting him a body that had already been abandoned by its soul (I'm also not so sure she didn't store Tyler's soul somewhere else. I guess we'll see!).