Listen to the orchestra. Listen for what isn’t there when she calls for supernatural help. Sometimes... silence is the most compelling dramatic statement when it comes to music.
And if you are as blown away by the vocal acting of the Alcina, run to the music store near you and buy the Archiv Produktion CD set of the opera starring Joyce DiDonato in the title role (with Maite Beaumont, Sonia Prina, and Karina Gauvin). It is the only recording of the opera done at Baroque pitch and with a mezzo-soprano Alcina.