Since it is confirmed that it was a flash drive I think that Shawn Adkins used his mom's computer and put the porn on that flash drive.
And I agree whole heatedly that we can't assume that Billie would have known about it. I still say that the jump drive belongs to Shawn and that maybe it was hidden her drawer unknown to her. I can tell you my mom doesn't even use all of her dresser drawers.
Yes, but to chose her bedroom dresser drawer when he had other places he could have hidden something. Men never know women that well enough to be able to predict when they might go searching for something, especially in their own bedroom.