More than likely it will be an off-duty officer in or out of uniform and he/she has to respect your privacy and your rights regardless.
Unless she's the state governor, it will undoubtedly be an off-duty officer and out of uniform (although many--if not most-- off-duty officers in the US do carry weapons on them).
I'm just wondering how much scrutiny should he be willing to but up with? What if the guy she bring is a fake police officer? How is he supposed to know the guy is real? What if the guy is a hothead and gets set-off for no reason?
He has a right to protect himself, as well.
I don't understand this point of view. The OP himself suggested that she bring an escort. Now we're only talking about what the escort does for a living.
Some women have truly scary friends, or friends willing to be accomplices in a false sexual assault charge...that's the kind of thing photographers have to be careful of these days (one female photographer was killed by her supposed client last year). What if she had said, "I'm bringing my drug-dealer boyfriend?"
An off-duty police officer is likely the best escort she could bring for the safety of both of them. Certainly nothing to be afraid of.