She giggles around your rod as you praise her so, and she proceeds to just that she once again takes you all the way down to the base, remains there for a few seconds, and then slides back up to the tip only to repeat the motion again and again and again.
It's at this point that you hear another moan, a familiar one, from the kitchen door… But your heads a little focused on what your mother is doing to care that it sounds like your sister has finally come home and discovered what you're doing.
Spoiler (click to show/hide):
I'll let you pick a picture for your characters sister