Start by pulling at the mirror to test the strength of the adhesive and where it may be located.
Remove mirror from bathroom wall.
Cover the mirror with duct tape.
The duct tape will limit the amount of glass that drops if the mirror shatters.
Protect the sink area.
Spread a heavy.
With another shim beneath your pry bar to protect the wall gently begin working the bar behind the glass.
If your mirror also has mirror clips you will have to unscrew them before you can remove the mirror from the wall.
Dress appropriately to prevent any injuries.
You can also use a small heat lamp.
Gently work along the top and sides of the mirror releasing a little bit at a time.
Quick tutorial on how to remove mirror from bathroom wall drywall or where ever.
You may want to use a heat gun and heat the mirror to try to soften and melt the glue between the wall and glass.
Maintain a steady pressure and listen for the drywall paper tearing loose from the wall.
Lay down cardboard or plastic on any surface surrounding the mirror.
Dress in long sleeves long pants and work boots to protect skin.