Use 'melodramatic' to describe someone who reacts too strongly to minor problems. She was being melodramatic about the broken nail, as if it were a disaster.
Pro Tip 2/3
Critique Behavior
It can be critical, suggesting the behavior is unnecessary or inappropriate. Stop being melodramatic; it's just a spider, not a monster!
Pro Tip 3/3
Not Literal
Often used hyperbolically to emphasize how someone is overacting. His melodramatic groan made everyone laugh during the game night.