Gabriela Gomez has been charged with felony arson for Monday's blaze. The fire destroyed a 1960s grand piano and other items valued at over $15,000.
Police say she was caught on surveillance video near the amphitheater where the piano and part of the stage was burned.
There have been seven fires at the nonprofit center since January. They started small, damaging a garden cart and later a couple of trash cans.
Detectives are still investigating to see if Gomez is connected to the other six fires at the property. Anyone with information is urged to call Fullerton police at (714) 738-6800.