Is it obligatory to compel the fiancée to wear the hijab after the marriage contract, or should she be left to take this step on her own, knowing that she acknowledges its obligation?

The hijab is a divine obligation that protects women and preserves their chastity and purity. If you exert effort in advising a girl and she does not respond, it is better to leave her and seek one who is religious. However, if you marry her, you must compel her to wear the hijab and prevent her from going out unadorned; for qawamah (guardianship/headship) necessitates preventing one's wife from committing forbidden acts.