Ever since Kate overheard Anthony speak about marriage in a not-so-gentlemanly way, she's made it her mission to stop his courtship to her sister, Edwina. On the outside, things between the two seem hostile at best, but Kate and Anthony know their hostile feelings for each other are turning a bit more romantic. In Episode 4, the Bridgerton family invites all of the Ton, including the Sharmas, to enjoy a ball at their country estate. After days of spending time together, Anthony and Kate are in the midst of a lust-filled argument in the library when Daphne bursts in, completely breaking their pent-up tension.
Of course, Daphne didn't ruin Anthony and Kate's big moment on purpose, but nonetheless, her interruption stopped them from finally crossing the line from enemies to lovers. The entire episode is filled with sexual tension from Anthony and Kate, from the lord nestling up to Kate to show her how to shoot to their romantic dance. It seemed things between Anthony and Kate were finally coming to a head, and they would reveal what they actually felt for each other in the library scene. That's why when Daphne walks in, it's such a disappointment. It's also the moment she realizes her brother feels much more strongly for Kate than he does for her sister, whom he's supposed to be courting. She spends the rest of her time trying to convince Anthony to be true to his feelings and to Edwina.
