Is it permissible for a girl to express her love to a man, and if work circumstances necessitate their interaction, how should she deal with him, or should she leave the job?

Working in a place where men and women mix in an unlawful mingling is not permissible except out of necessity, while adhering to the full legal hijab, which includes covering the face. If the man is religious and of good character, there is no harm in sending a trustworthy person to him to inform him of your desire for him to propose to you through your father, without revealing any love to him. If he does not respond, then it is better to leave this place.