An overpowered device, be it an iPhone or a magic mirror, is a recipe for disaster. At first it's the utility of the thing. Sometimes you NEED to check your e-mail on the go or ask a demonic visage for updates on the kingdom.
But then the inevitable abuse begins. You start checking football scores at red lights. You fire up "Angry Birds" at your brother's wedding. In a moment of waning self-confidence, you even ask your magic mirror to rat out pretty girls so you can deploy axe-wielding henchmen to cut out their hearts.
That's exactly the trap our queen fell into. Jealously protective of her status as "the fairest of them all," she used her mirror to magically e-stalk her rival. When her huntsman failed her, she turned to even darker magic, twisting her appearance into that of an old hag and gifting Snow White a bevy of lethally cursed items: a haunted corset, a toxic comb and finally a poison apple.
In the end, her murderous attempts failed. Depending on the account you read, she either died a twisted hag, pursued by murderous dwarves, or the sadistic Snow White forced her to dance in red hot iron shoes at her wedding.
The lesson: Whatever the details of her downfall, the queen's fate was avoidable. Let well enough alone and don't use your magic to pursue petty vendettas. Just turn the smartphones off, set the demonic mirror aside and read a book or something.