Final answer:
The sentence 'she was white as a sheet' contains a trite expression, which is an overused phrase that lacks originality.
Step-by-step explanation:
The problem with the italicized element in the sentence 'she was white as a sheet' is that it is a trite expression. A trite expression is a phrase that has been overused to the point that it has lost its original impact or significance. In literature and writing, these expressions can be perceived as a lack of creativity or original thought.