When father-in-law and daughter-in-law were supposed to be handing out candy

My stepson brought his fiancé over because they like our neighborhood to go trick-or-treating. She said she wanted to stay and help me hand out candy so that she could get to know me better. After we ran out of candy. We went inside and she said she had something sweet for me. Next thing I know she gets naked and puts on a mask and tells me to eat her pussy. How can I turn her down?