This study investigates the impact of reflective questioning by human visitors and AI-powered virtual assistants in digital museums. Reflective questioning, which encourages deeper engagement with exhibits, enhances cognitive processing and emotional involvement. The study consists of two parts. In Study 1, a one-factor between-subjects design is used to compare the effectiveness of reflective questioning posed by either human visitors or AIVAs in a controlled online museum environment. Study 2 further explores the mediating roles of emotional engagement and mental cognition that contribute to attitudes toward the conversation. The results show that emotional engagement plays a partially mediating role in the reflective questioning and attitudes toward the conversation. Human-initiated reflective questioning fosters stronger emotional engagement, whereas AIVA-driven questioning has a less effect. This research advances the understanding of AI-mediated engagement in digital museums and offers practical insights for designing interactive museum experiences that foster deeper visitor involvement.