I never quite get it when a wg offers owo but not cim. In practice she must end up with a certain proportion of punters cumming in her mouth because at the end of the day, ejaculation is a reflex. Even with the best of intentions, one could cum suddenly and without warning. Personally, if I had booked such a girl, I would go with covered oral. I'd rather not piss a woman off while my cock was in her mouth !