How can you fix a bad dye job?
Ideally, I’d tell her to go to a salon– double processed hair is pretty hard to fix.
If that’d not an option I’d tell her to use a low ammonia/ low peroxide haircolor in a shade or 2 darker than what she is aiming for–colored/overworked hair is less pourous and therefore will take color a lot less well (as evidenced in the fact that the 2nd dye job didn’t quite take)
Also, it may just be the shade of blonde that she used that is to blame. In this case, using a toner might be a good option (look for them in beauty supply stores like Sally’s)
If it is too reddish, I’d suggest counteracting this using a beige or ash blonde toner. If it is greyish/dull looking I’d suggest warming it up with any color that is labelled “Golden” or “Warm”
Hope this helps