sounds like the place was pretty scenic. Not suprised a couple would want some photo's there. I think since the place is public, she was as right to ask you to move as you were to be sitting there. I think she could have handled it better, though.
But then, It's possible that she was dealing with a hard to deal with couple who were giving her a hard time, or she was in a not so plesant mood, or something. But then, if I was in your situation, I'd probably be a little grumy imwardly, as well.
But anyway, on a different note, I hope your project is going well