How does Juliet discover she has fallen in love with a Montague?

Juliet discovers she has fallen in love with Romeo, a Montague, during the Capulet's feast when they share a passionate kiss. After learning his identity, she is initially distraught, realizing that their families are sworn enemies. Despite the feud, her feelings for him deepen, highlighting the theme of love transcending social boundaries. This moment marks the beginning of her internal conflict between her love for Romeo and her loyalty to her family.