Is the female employee sinful because of her previous work which involved extensive mixing with men?

We ask Allah to replace your current job with a better one, to expand your provisions, and to grant you a righteous spouse. Mixing [between genders] is of two types: forbidden, which is the predominant type, and permissible, which has been detailed in fatwa (definition) number: 48092. What you mentioned about men cleaning the prayer room and restrooms has no legal impediment, provided it is free from the prohibitions of unlawful mixing, such as khalwa (definition) (private seclusion) and the exposure of awrah (intimate parts). If you have done anything displeasing to Allah, you must repent sincerely, for "the one who repents from sin is like one who has no sin." Charity extinguishes the wrath of the Lord, and the soundness of one's religion is more important than the soundness of one's wealth. "And whoever fears Allah – He will make for him a way out and will provide for him from where he does not expect."