Was Cheri's murder premeditated?

I might be wrong, but I don't think that it was. We know that her car had been tampered with so that it would not start. We not that Cheri walked off with her killer. Why? It had to have been someone she knew and/or was not afraid of. Here's what I think happened...

The killer tampered with Cheri's car so that he could give her a ride home (or maybe walk her home... not sure how far she lived from the library) and ask her out on the way. When they were walking, something they were discussing pissed of the attacker and he lost it. I'm guessing Cheri told him that she had recently gotten engaged and the killer became furious. The murder was pretty brutal, as though the killer had gotten very angry. He slit her throat damn near to the point of decapitation, and he did so with a shitty pocket knife. I don't remember exactly how many times Cheri was stabbed, but it was enough to make you think that the killer snapped for whatever reason.

In other words, I do not think this was a premeditated murder.