It was actually more than 15 minutes, by the spa's own rules.
And I tried to get her fired because of her attempt to cover it up (before I even caught it), meaning it was an overt attempt to cheat me rather than a human mistake.
I will admit to trying to get people fired when they either cheat me or are outright confrontational with me.
You may not agree with these actions, but it doesn't make me paranoid. And complaining to an employee's superior is actually the RIGHT way to go about these problems. It's not like I find out where they live and vandalize their property. THAT would be an overreaction and the sign of someone psycho.