Is OTHER wrong in the post ? POST : I'm writing this on mobile, so apologies for any wonky formatting!

I'm a college student and I live with three other amazing girls, including one girl who's been my best friend since we were 12. We're all really close, more like sisters than friends.

My best friend has a bad habit of leaving her laptop open and running while she's away, and while this mostly happens in our dorm room, she's been known to do this around campus. I have repeatedly warned her that this isn't safe, as not everyone is trustworthy and people might see an open, unlocked laptop as free real estate, and claim it as their own. She rolls her eyes and says that she only leaves it open in our room, but I know that's not always the case as I have come across the laptop on occasion while my friend is no where in sight.

So, I've taken to trying to teach her a lesson. Whenever she leaves her laptop open and running while shes away for atleast an hour, I change her background. Usually it's either pictures of feet (she finds all feet revolting, and therefore hates Quentin Tarantino films), or various pictures of our lord and savior, Shrek. She's been leaving her laptop open less and less and since I started doing it, I've only come across her open unlocked laptop once in the wild of our college campus. 

It's been a few months since the last incident, but about 30 minutes ago she scampered off to an hour long meeting and left her laptop open, unlocked, paused on a Backstreet Boys video. I could not resist temptation, and her background picture is now a picture of Barry B. Benson from the critically acclaimed Jerry Seinfeld movie "The Bee Movie." 

So Reddit, I ask you, am I the asshole for changing my friends laptop background despite how much it annoys her?