Way to go in telling her off! You were right if she watched the whole thing for 20 minutes. She was upset at herself being fascinated by it. Otherwise she'd have yelled, walked off, and or probably called the police on you. Do you think she recorded you, or your plates? Maybe don't use that exact spot again unless you have a better lookout view?
A few years back I met up with a guy at his place around mid-morning. We talked for a bit and then proceeded to his bedroom where we both undressed. Almost as soon as he lay back on the bed, his phone rang. He got up and answered it, telling the person that he was still on for tonight. As he returned to the bed, he explained he was going out with a female friend later. I moved to between his legs and began kissing and caressing his balls - touching him all over. He wanted a long session of edging before he came so I would suck his dick for a while and then move back to licking/sucking his balls. He was quite verbal and was letting me know how much he was enjoying this. I would suck on his dick until he was close and then change it up some. I began rimming him and he loudly professed his admiration of my attention to that area. We had been involved for about 30 minutes and he said he really needed to cum. I took him into my mouth and began sucking in earnest. He was moving his hips. wiggling around and telling me how wonderful it felt.......and then he froze. Behind me I heard a woman's voice telling him that this is a surprise. I sat up and saw this lady standing a few feet from the bed and looking at us. She said "Don't let me interrupt" and just stood there. As the guy lay back, he reached up, and took me by my head and guided it back to his dick. He let me know he had to cum now. I was quite nervous but began sucking again. I felt her sit on the edge of the bed as he went back to his loud, lusty encouragement as I was eagerly sucking his dick. I could feel it swelling up and he let me know it was ready to explode. In just a few seconds my mouth was filled with an immense amount of cum. I kept sucking and swallowing as he kept spurting more into my mouth. As he finished and I was slowly sucking the last bit out of him, she placed her hand on the back of my head and told me that I was an excellent cocksucker. She explained that after calling him, she thought she would just pop by and visit for a little while. She had a key and said that when she opened the door and heard all the noises and sounds he was making, she had to see what was going on. I put my clothes back on, told them that this was a totally unique experience for me, hugged them both, and left.