She may have gotten Dave killed, but I am not sure if it was all in fun. Her entire shtick is Justice. Meaning she dispenses Justice to her enemies/bad guys. That was the reason why she left Vriska in the first place; Vriska killed people that weren’t “bad guys.” Screwing with bad guys is her idea of fun.

But with Dave, he didn’t do shit to be a “bad guy” at all. So Terezi didn’t kill him out of her “fun moods.”

I think that, since she saw his whole future, knew that it was an offshoot that died. She was trying to stall Dave learning about the god powers because if he found out about it, and he did go to the bed, Jack might have killed him off of the bed and thus permanently kill Dave.

So like, no matter what choice she did, Dave had to die. Just a thought on that, on at least what I think.