Huh...yeah, that's definitely possible. So he could have actually been killed later than we think he was.

...but what'd be the point? She doesn't have an alibi from nine PM Tuesday until 8:30 AM Wednesday, and that's when Dave had to have been killed if we take his cold body at face value. You'd think if she wanted to alter the temperature, she'd make it so that it seemed like he'd been killed while she did have an absolute alibi.