An outside object would do the trick and cause an infection.
Every person has their own thoughts and feelings about stripping an animal for she calves, kids, lambs, etc.
If your vet is suggesting it and he knows what the case is (she is dry and is "due" in June) then I would urge you to follow his lead. He is the one you will go to for help when you need someone in the flesh. It is best to keep a good relationship with your large animal vet as they are few and far between. :no:
You could strip her out, dip her and then keep a close eye on it when she calves.
I dunno. It is up to you. When our cows are dry we don't mess with them until they calve.
I am also overly anxious when it comes to our animals...sometimes it is nothing and then there are times when you know something was happening but you didn't want to get pegged as overreacting and then something goes wrong (lost our oldest doe this year, that way...).
You know the animal and you can sense when something is wrong. Follow your instincts...can't say it enough.