Selma police say 39-year-old Jeannie Small invited the man to stay with her at a house on B Street.
On April 11, Small accused the 65-year-old man of stealing her belongings, officials say. The two started to argue, and then Small pulled out a gun and held it up to the victim's face, saying she would shoot him if he didn't leave.
Police say the victim left his $270 mountain bike, $185 in cash and other personal items behind, and reported the robbery a week later.
On Monday morning, officers found Small outside the house and arrested her for armed robbery and violating parole.
Investigators also discovered Martin Delacruz, a known gang-member, trying to run away from the home, but he was taken into custody after being found with tear gas.