What should a Muslim girl do, who was raised, educated, and worked in mixed environments, which were imposed upon her by her parents, in a society where mixing is prevalent?

If there is no necessity for a girl to continue in a mixed-gender work environment, then it is obligatory for her to leave it. It is not permissible for her to get accustomed to mixed-gender interactions from a young age. She is not permitted to obey her parents if they order her to continue in it, because there is no obedience to a creature in disobedience to the Creator. However, if there is a necessity for her to continue in it, then there is no harm, provided she leaves it when the necessity ceases and observes the শরعي (Shari'i) guidelines.