Not sure yet, about 6 months ago she stayed at a friends for a few days and when she came home she had bleached her already blonde hair

even blonder. I wasn't happy but as she was blonde anyway it didn't look too different.
I told her NEVER to touch her hair again.
Well yesterday she came home from a different friends and she had tried to dye bleached blonde hair brown.
Today in the light it is a plum colour and we have had major tears this morning.
I am going to ring the hairdressers explain all and see if they can do anything. No pocket money for her for a very long time!!
Why do teenagers do these things????