。
Her manner of speaking is extremely commonplace.
Literal
She [topic-は] manner-of-speaking [subject-が] extremely commonplace.
話し振り (はなしぶり) uses the suffix ~ぶり (~振り, 'manner of doing'), which attaches to a verb stem to describe how something is done — related to but distinct from ~方 (~かた). 極めて (きわめて) is a formal intensifier meaning 'extremely.' 凡俗 (ぼんぞく, 'commonplace, mediocre') is literary vocabulary rarely used in everyday speech.