I think the point is that she gets flustered, but she's not mediocre at all. When she's not worried about failing things (failing to impress Dorm-masters or examiners) her cooking is great (stuff she does for the students in her spare time).

She is talented, but the way the school pressures students with the constant threat of failure doesn't mix with her.

Aside from changing the recipe, her Terrine warrants pass material.