Is my wife considered sinful for having falsely sworn before a judge that she owns a share of the pharmacy, while she is merely responsible for it in exchange for a monthly wage, and what is the way to absolve oneself of this sin?

If a wife swears that she owns 75% of a pharmacy, while in reality she owns nothing, this is a forbidden "yamin ghamus" (a false oath taken intentionally to usurp the right of another), and she must repent to Allah; no expiation is required of her. There is no objection to an agreement with a female pharmacist to open a pharmacy, with capital from the pharmacy owner and utilizing the pharmacist's certificate to obtain the license, in exchange for a known salary for her, provided that the person managing the work in the pharmacy is a specialist to avoid damages that may result from ignorance of medications. If this condition is met, the wife can continue working in the pharmacy along with her repentance; otherwise, she must leave it unless the buyer commits to employing a specialist.