Hair colour went wrong, what should I have done?

[juli]

hello hair geek im new here.i need some help with the colour
i had a client with really light blonde and she wanted coper lowlights so i used 7c in matrix but her hair went kind of pink can anyone tell me what did i do wrong and how it should be done .thanksss

 

[AcidPerm]

Are you a qualified hairdresser? Did you pre-pig the hair? What was her original base?