Inappropriate conversations

There have been quite a few conversations I’ve had recently with a certain person that I really do not know that well. I don’t start the conversations, nor do I lead them anywhere, but she persists on bringing up somewhat inappropriate comments/stories/questions. When I begin to hear them I internalize my cringe reaction, and swallow the caustic sarcasm that so often surfaces to my tongue. What do I do? I’ve attempted avoidance when possible. I try hard not to laugh. I am soooooo tempted to fabricate a horrifyingly inappropriate conversation/question for this person just for my own amusement – but I’m worried what else could possibly be unleashed. I’m not one to be grossed-out/prudish/ultra-religious……but damn, there are some things that should not be shared…..with anyone.