There's a scene where she's midway thru fucking a younger guy and he jokes that she probably hasn't seen any action for 20 years. She looks at him and says, "you don't know where I've been" - one of the hottest things I've ever heard from a mature woman!
Mother-in-law wants her space so she gives her son-in-law a mind-blowing sexual experience and hopes he'll go back to her daughter and patch up their differences. Son-in-law now knows that his tight-bodied mother-in-law that he secretly fancies is up for sex pretty much anytime while warm memories of his penis disappearing and reappearing out of her mouth and pussy fill his mind 24/7. Great storyline, great action.