Hi, I saw this post and thought maybe I could help with products for this...
You could try a creme lightener as that isn’t technically bleach and you’re client would be none the wiser!
If you choose one with that brands version of ‘Plex’ technology, she won’t even notice that it’s been lifted a few levels.
Just tell her it preps the hair for the colour...
Lift to a 6 and then deposit the shade you’d like.
It’d be a lot more true to tone than lifting with a colour in my opinion. It’s more work, yes, but if you can get an even coppery undertone base, any level 6 you put on there (brunette or red shades) will look lovely and will fade beautifully.