Spanking daughters

I am a single father of 19 years old daughter. I divorced form my exwife more than 10 years ago. Since than my daughter lives with me. It is my responsibility to discipline her. I spank her on regular base. She agreeded to be spanked from the very first day of our living together. Very soon after starting to spank her, I saw something not so usual. Her nipples were erected even before spanking. And she wanted to be spanked more frequently! Not much after that, she proposed to be spanked on bare. One day she simply took off her panties and laid across my lap! She is an adult girl now, but she insists to be spanked on regular base. She asks for it; sometimes she asks to be spanked every evening. Any other parent with such experience, or like to comment?