Friend sister

Hey I had bad situation and need advise Or positive words to support me

Shortly I was at my friend's house. We've been friends for over 20 years. He asked me to go to his house to help his wife while he was away traveling. I am required to be there while a maintenance center is repairing water pipes. While I was there I was surprised that his little sister was there. She old 29 and she married. After finishing with the maintenance workers, she suddenly stroked my penis without saying a word and looked into my eyes. She whispered in my ear and said, “I wish you were my husband and this sleeping monster entered me.”I lost my speech due to the shock. My heart is shaking, all my limbs are trembling I ended the situation by running to my friend's wife and children and saying in a loud voice that I was leaving. My feelings are mixed and I don't know what to do. Should I go with my feelings and enjoy them and lose my childhood friend or should I abstain from them?