Hi, Dream lover just a suggestion....
but do some test pieces on this first ....
I think you would get a better result if you spent some time with a thick conditioner and talc mix .... picking out and wrapping tightly all those whiter bits of hair in foils to protect them as much as you possibly can, you can do this by extra folding in half then fold the sides in as usual .... then fold over and over again till its quite tight and wont move about
(its only talc and conditioner so you don't have to worry about marks)
then go in and bleach up those yellow parts to a creamy blonde then rinse the bleach from between foils being very careful no bleach gets inside those foils .... if it does rinse towel dry and apply a new foil with conditioner and more talc mix
then towel dry off and apply 0/6 wella colour fresh silver based toner to freshly bleached hair only .... roots first ends last,
( you dont need to tone the white bits ) they will look very nice on the new cooler hair tones ,
This procedure is time consuming but I think it will be worth while doing
as it will get rid of those yellow problems once and for all ,
do you think there's a possibility of weaving out all of those white bits ?
there may minor strands of of breakage,
but it should be very minimal depending how well you can wrap and protect the white hair against the bleach ?...
Ps .... you may need her to sign a disclaimer
do some test pieces first to see what results you get on the yellow parts
and time it well ,
Also Dream lover .... proclere toners are very mild toners that do not produce grab
and as you know if you use anything stronger on very white bleached hair you will always run the risk of grab .....
also if you use peroxide based toner each time you try another..... you are simply risking the condition of those whiter bits and breakage may occur.
This lady needs a good maintenance programme from the pureoligy range especially if she is always shampooing her hair !.
as no toner will hold as you are finding out yourself ....
ask persianista about the pureology range as it helps colour from fading
plus ..... you are always going to have problems with those white bits until they grow out !
also until it grows .....
you can always spend some more time weaving out some white bits again throughout the top and protect them in foil before toning the whole head again so it wont grab
hth a bit more
minky