Sorry I didn't see your post before I posted the exact same thing!
I agree with both of you,
I think it was premeditated. If a mother's baby accidentally dies, the normal reaction is to call 911 immediately and try to save the baby. Not to cover it up for 31 days.
But to actually prove solid premeditation, usually the court requires some amount of time between the planning and the killing. For example, in a case where a man murdered his wife's lover, he found out at 8am that she was cheating on him, and didn't kill the lover til 10pm at night. The court held it wasn't premeditation because he was "in a rage" that entire time and wasn't thinking straight. If I can find my old crim textbook, I'll find the citation for the case.
Here, her google searches show premeditation more than the duct tape. If KC just exploded and put the duct tape on, its not necessarily considered "premeditation" under the law if it was all done in one act. BUT, because as you pointed out the duct tape itself is likely to kill, putting it on is attempted murder, and her subsequent dying could be manslaughter at the least - but its still considered Murder 1 / Capital Murder.
Its kind of complicated the actual steps to prove murder, after a year learning it we all were -> :banghead::banghead: