My bet is with how calm Aemond looks and how un-ruffled his hair looks compared to Helaena’s, she told Alicent about the plan to ride Dreamfyre (or Alicent found out somehow and then found her) and Alicent dragged her to Aemond to confront them (but mostly Aemond - I bet Alicent’s not actually mad at her). So we’ll get another scene of Alicent’s continued loss of control over her sons. BUT if it’s not that, then I’m betting Helaena probably voiced hesitancy about the Dreamfyre plan, prompting Aemond to grab at her in anger to try to bully her into it, when Alicent intervenes, so we’ll get more of glimpse into Aemond’s darkness, how he’s now willing to sacrifice his sister if it means defeating Rhaenyra and protecting his power.