I believe the device is on the side that you only see your own reflection, but I could be entirely wrong. I base my assumption on the premise you can see the contents of the tablet from your side.
As I understand it, one-way mirrors let light pass in both directions. To be used as a "one-way" mirror it relies on the light differential between the two sides. Namely, it will always look like a mirror to the brighter side and like a window from the darker side into the brighter side. So, technically, the "mirror" side is facing you wherever the screen is dark on the other side. When the screen is bright, then the mirror works as a window. The problem is that I am not sure how bright is bright, i.e. would a normal color photograph, displayed against the mirror panel from the other side, be too dark to be seen through?
Also, I am not sure of is if it distorts the image in some way to have the mirror panel in between the device's camera and the outside.
Two way mirrors can actually be seen through both sides given the right lighting. Here is more information from MentalFloss https://youtu.be/XKuF1eT1Cqc Given that, I am sure the camera could see out, which in a bathroom could be a much creepier feature than if it couldn't.
Also, I am not sure of is if it distorts the image in some way to have the mirror panel in between the device's camera and the outside.