Sorry, you're wrong!
She has done a good job and
has not plagiarized!
She has identified his source at the beginning of the paragraph,
letting readers know who is being quoted and has provided a
footnote directing them to the exact source
of the statement.
She has paraphrased some of Boorstin's
words and quoted others, but makes it clear to the reader which
words are his and which belong to Boorstin