It is hard to fake it with an orchestral harp because it is played with the balls of the fingers. South American Harps are played with fingernails. So its a much thinner and more percussive sound. And the construction is different. Whereas orchestral harps are built solid and heavy, South American harps are light, almost like balsa wood, and resonate more.
If you want to "fake it" you would probably get a more similar sound with a picked nylon string guitar, with a nice resonant body, and slightly detuning, applying EQ and arpeggiate your chords. See if that works.