These types of stories are inappropriate. We should respect the privacy and dignity of others, especially in the context of a marital relationship. Publicly sharing or discussing such explicit scenarios is unethical.
This is inappropriate behavior. You should have an honest and calm conversation with her about how this makes you feel and the inappropriateness of such actions in public or around others.
Maybe in the fictional story, she was under the influence of some mind - altering substances that made her lose her inhibitions. Or she could be trying to make a point in an extreme way, perhaps to get back at her husband for some wrong he did to her.
No, it is not appropriate at all. Such a description involves disrespect and objectification of a woman. We should respect others' dignity and privacy, regardless of the situation.
Well, obviously the women are main characters as they are the ones doing the showing off. And of course, the plumbers are also main characters since they are the ones the women are showing off for.