Al-jawab billahi at-taufeeq (the answer with Allah's guidance)
It will not be permissible to work in such places where free mixing and intermingling of sexes takes place.
She should work in places where there are women working and also wear the complete Hijab and act with modesty and dignity.
Allah Says : "O Prophet! Tell your wives and your daughters and the women of the believers to draw their cloaks (veils) all over their bodies (i.e. screen themselves completely except the eyes or one eye to see the way). That will be better, that they should be known (as free respectable women) so as not to be annoyed. And Allâh is Ever Oft- Forgiving, Most Merciful." .
Allah also Says : "…And let them not stamp their feet so as to reveal what they hide of their adornment. And all of you beg Allâh to forgive you all, O believers, that you may be successful" [24:31].
He also Says:"…then be not soft in speech, lest he in whose heart is a disease (of hypocrisy, or evil desire for adultery, etc.) should be moved with desire, but speak in an honourable manner." [33:32].