The Monroe County Sheriff's Department said Nicole Ingram Dobol, 26, found her ex-boyfriend's roommate at Hog Heaven Bar and Grill in Islamorada Nov. 19 and asked about where she could find her former lover and the man told her he had gone home.
Investigators said the man also told her not to visit the apartment, but she allegedly forced the door to the apartment open and went to her ex-boyfriend's bedroom, where she discovered him asleep with another woman.
Dobol allegedly set fire to the mattress while the couple slept and taunted them when they woke up.
The couple, who were not injured, took the mattress out to the apartment's balcony and extinguished the flames.
The man's roommate, who arrived home during the incident, said Dobol told him it "made her crazy" to see her ex with the other woman, so she set the fire.
Dobol was arrested Wednesday on an outstanding warrant and taken to jail on charges of arson and burglary.