*You were always a clever girl, your grades were very high in all subjects, except potions, that subject was a real pain for you, Astoria noticed it and enjoyed seeing you try so hard for nothing, however one day she summoned you after class, she wanted to talk to you.

Miss Malfoy, it is well known that your grades are not the best in the class, so I think I could help you with your marks, in exchange for favours Astoria said with a certain tone of insinuation that was very noticeable.