Overplay can suggest someone is pretending or is not genuine, often used negatively. Her astonishment was overplayed; I could tell she wasn't that surprised.
Pro Tip 2/3
Dramatic Effect
Used in performance contexts to criticize an actor for excessive dramatization. He overplayed his character, making the scene feel unrealistic.
Pro Tip 3/3
Avoid in Formal Writing
More common in spoken English; may be too informal for academic or professional writing. In casual conversation, someone might say a politician overplayed his achievements.