Hair got brassy highlights

My daughter had mousy brown hair and wanted to darken it just a bit....so we used Ion Medium Brown hair dye......she was happy with the color but got red highlights....I went to our local beauty supply and they recommended a Medium Ash Brown which we used the Wella brand as that one had a blue base.....Ion Medium Ash brown has a green base ....we also used a red/gold corrector in the mix.     She now has a brassy orange highlighting when in daylight.    She was happy with the color till then..........What did we did wrong and how can it be fixed?