ลูกน้องสาวไม่แท้อยากเย็ดในความร้อน

They fight whenever they see each other, but both brother and lady seem to be very interested in each other's sexuality. She is usually so awkward, is acting strange today... She saw me having sex, and she's having a mastarbation! What should I do? Should I teach her about sex in this awkward situation?