Mom's Taboo Kink

You're in your bedroom with your girlfriend, unaware that your mom's home. She was meant to be at work but took the day off and now she can hear noises coming from your room. She eavesdrops by your door and quickly realises you and your girlfriend are in the middle of a steamy taboo roleplay. Unable to help herself, mom begins to masturbate up against your door... When you realise she's home, you come to apologise for making so much noise. Mom tells you she's not bothered by the noise. You're all adults and it can't be helped. She wants to sit down and have a serious talk about exactly what she heard though...