Very ashy medium blonde on client with balayage

[HorridHenry]

Hello,
I’ve got a client which is between base 6.1- 7.1 naturally and about 30% grey ( mostly at the front). She really likes the balayage effect and hates highlights, so I do some balayage with l’oreal studio paste. I really struggle with her root colour though. Her hair always comes out quite warm or gets warm after couple washes and she really wants only a very cool blonde. I already tried Majirel 7.1 + 20 vol ( was bit too dark for her on the beginning, got very warm after 4 washes and afterwards it was quite hard for me to lift it to a nice light blond with balayage) and now I’m using Luo 8 + 7.1 and sometimes a bit of blue mix ( again, it’s nicely ashy on the beginning, but today I’ve seen her after 1,5 week from having colour done and it’s already very warm!) Do you have any ideas how could I get on her colour between 8.1-7.1 which would last a bit longer but wouldn’t be a nightmare to lift afterwards?

 

[EssexFreelance]

What is she washing her hair in?

 

[AcidPerm]

If it’s fading very quickly, either the hair is very porous and/or she’s not using salon quality products.
I usually point out that they’re wasting their money to pay for a good colour service to then ruin it using cheap shampoo.