How Does Your Girlfriend's Thong Look on Your Stepmommy?

My stepmom asked me for a favor, but I didn't think she would ask me for advice on her lingerie. When I walked in and saw her looking that hot, I still tried to play it cool, assuming she only wanted my help to impress my dad. Things started getting weird when she took off the first set of lingerie to try on the next one and let me see her tits! They were firm, perky, and big. I wanted to hide my face in them, but I knew I had to keep it together. Then, I recognized the thong she was wearing. It belonged to my girlfriend! That's when she finally confessed that she spies on me while I have sex with my girlfriend and gets turned on by it. She wanted me to show her what I can do, so she took off my pants and didn't hesitate before shoving my dick inside her mouth. I tried to stop her, but she was sucking it dry and the feeling was too good for me to do anything else besides moaning. She licked the entire thing and took it deeper in her throat than anyone else. She even smacked her massive boobs with it! If she was going to let me pound her on all fours and cover her face in my cum, how could I say no?