i was in the same situation, except the test wasn't out yet.
i purchased a squeeze chute that my vet could do a c-section on. luckily, she was free, and so was her heifer. they were both from known carriers.
i think what i would do is find a way to take a hair sample of the calf via surgery as early as possible. there must be some way to take the equivalent of amniotic fluid and test the developing fetus.
this must be cheaper than the video we saw earlier.
there is a component of what you should do. hmmm. i would advise the options and let them decide, gladly take their money for the choice they choose and display no malice for their blunder. at this point, some people don't need to hear a speech, others need information. they might be a customer for life if you can guide them in a direction that minimizes their losses and will look to you to give them choices on what to do rather than deciding for them. i'm not in public relations, but have found recently that talking quieter when others are screaming is effective. it took me about 40 years to learn that. i retain an exemption on this method for politics, though i guess obama is proving me wrong on this as well.