Jodi Arias trial: Does state of Travis Alexander crime scene show lack of premeditation?

I've been playing devil's advocate tonight, especially now that the defense has requested that Judge Sherry Stephens allow the jury to consider a lesser charge of manslaughter in the death of Travis Alexander. Those following the case will readily recognize that prosecutor Juan Martinez has stated Jodi Arias premeditated Travis Alexander's murder in an elaborate plan.

According to the prosecution, Jodi Arias was an obsessed, jealous stalker who dated Travis Alexander in Feb. 2007, then continued to force him to have sex with her until June 2008. She stole a gun from her grandparents in May 2008, planned a long-distance trip from Yreka, California to Mesa, Arizona, where she borrowed gas cans from an ex-boyfriend, rented a car 100 miles from her home, drove to Travis Alexander's, forced him to have sex with her and took naked photos of him (he took nude photos of her as well), then brutally slashed his throat, stabbed him 27 times, and shot him in the head.

If Jodi Arias premeditated Travis Alexander's murder, to the point she planned it for weeks or even months, then why would she leave so much evidence in his home, leave a bloody palm print on his wall, and try to dispose of evidence by throwing a digital camera and clothing in a washing machine?

Are these the actions of someone who has premeditated and carefully or meticulously planned a murder?

Is it possible to spend so much time plotting a murder and leave so much evidence at the crime scene?

Do you think it is possible that the condition of the Travis Alexander crime scene may show that Jodi Arias did not go to Travis Alexander's home with the intent of murdering him, as she did not clean up the crime scene?