Why would I want to bust my children? I'm not a cop. I'm a parent.
Have you any comments about the fact that this kid lied to her mother?
Every parent is part cop and part judge, but they are also a number of much more pleasant roles. I would rather feel more like a teacher, mentor, role model, etc - but when your kid is repeatedly lying to your face, they've broken trust and there is consequences. How you find out about it really doesn't make a difference. Whether it's a tracking device, a phone call from another parent, a speeding ticket in the mail, or if you catch them in a lie yourself, it's a big problem.