Ok-so still start with stand alones and deep conditionings as her hair will be going through quite a bit for this look. So if she has more than 1" of new growth you have to apply 20
or 30 vol 1/4" off her scalp to match the gold. Then go back with 20 and lighten her 1/4" until it's even. All with Olaplex of course. It will save her hair! Then you'll have to evaluate where you're at. If her hair feels good you can use lightener with 20 on and near scalp and 10 on ends to lighten to palest yellow. Low and slow it the best way. Olaplex added to lightener and conditioning between lightenings. This could take more than one or two rounds. When it's all an even pale yellow you can tone with a 9V, 9T or 9P (I believe the stylist that did the Kardashians used Redken) You can find the formulas on Behind the Chair also i think. Hope this helps. Remember, don't push the hair too far or no matter what you use it will melt