Serious conversations are pretty standard between you and your Mom, but this one is definitely a new one. Mom stumbled on your internet history, and found that you have a particular interest in Mommy porn. She can't wrap her mind around it. However, she doesn't want to be closed minded - she's always telling you to be what you want, do what you want, as long as nobody gets hurt.
She wants to help you in your sexual interests, because that's just the kind of Mom she is to you. Well, she awkwardly teases at first, noting that you're getting excited. This reality hits her and she suddenly stops.
Talking herself back into the tease and ultimate orgasm assistance for you, she begins rubbing her pussy. You're so close, so excited! Well, you were, anyway