Can a father's glances at his daughter when she is adorned in front of him, which she dislikes, be considered a form of Qadhf (slanderous accusation), and if so, what should she do and how can she repent from that?

This statement is not considered an accusation of slander (qadhf) because it does not contain an explicit or implicit accusation of committing an immoral act. However, it is forbidden, whether the girl is truthful or a liar. If she is a liar, she has slandered her father and committed a great sin. If she is truthful, then it is her duty to conceal her father's fault and advise him gently, avoiding appearing before him in adornment that attracts his attention.