Motive: Much like everyone, Laurel has personal stakes in this situation. The thing is, though, she's more caught up in it. She's been snooping on Rebecca with Wes for a week or so. She sees what Rebecca did to Rudy.
Evidence: We know Laurel has had Michaela's ring this whole time, and she's managed to keep it a secret. That means she's good at hiding things, and she's not afraid to act if it means protecting herself. She's also the one who tries to keep Wes quiet while they investigate Rebecca.