Why does your sister flirt with your quiet boyfriend?

There could be several reasons your sister flirts with your quiet boyfriend. She might be drawn to his calm demeanor and find it intriguing, or she could simply enjoy the playful interaction without any serious intentions. It’s also possible she sees it as a way to tease or test boundaries, not fully considering how it might affect you. Ultimately, communication with both your sister and boyfriend can help clarify their intentions and feelings.