Obviously none of us were there to witness the exchange.
But I disagree with the suggestion she was unreasonable. Many professional photographers (several I know personally in corporate and wedding work) would be a lot more forthright in their directions. I think she's fairly good in her capacity to communicate subtly, even assertively. We all have our own ways of communicating based on experience. I have had my moments ushering stragglers out of my organised landscape shoot, and by and large, they are very happy to oblige, to which I make my appreciation very well known, to the point of thanking them personally after the shoot. A family enjoying a wonderful early autumn evening on the beach put down smack-bang in a scene I had been framing for 1 hour. I approached the husband and explained what I was doing. He, wife,three kids and dog happily moved away. Afterward, I thanked him and he responded, "no worried, mate" (well, this is typically Australian!). Diplomacy is much better than making a scene, and if somebody doesn't move, then the professional should just let it rest and scoot for another set up. Weddings elevate the photographer assigned to move people, members of the public, around and about so as his imaging is not impinged. In public places, people are not obliged to move for anybody, certainly not photographers and again, diplomacy wins the day even if you must go to lengths to qualify and assert the necessity for the person/s to move. Accept refusal gracefully and move on; it's only a photo. I've not had the frosty exchange that you had, but many times have issued a pointed finger to indicate "out of frame please!" (if people are distant), or just move elsewhere if people are clear they are not going to move (and some people want to be very clear).