If you were a close friend, I would tell you to muster some testicular or ovarian fortitude and not be a pussy and just stick it through. But I don't know you, and that's impolite and not Escapist etiquette.
As others suggested you could change the subject, and add some gross out humor to it yourself. If it really bothers you, be direct and voice to her to set limits. But really...they're just descriptions and talk, it's not the same as actually going through it yourself or seeing and smelling it. Laugh and live a little.