Slutty sister

I was watching a video on my son's phone of him filming my younger sister,in the video she walked over to the door and you can hear her say it's ok she's in the garden,she walks back to him and sits on a chair and tells him to keep an eye out for me,she's giggling and then i see his d*** come in to view and she starts sucking him off, you can hear her say you like mommy sucking your c*** and she pulled away as he quickly started to e********,does it mean he wants me.