Thanks for you report and comments, Matt.
While considering Bentley as the caller is intriguing, I have some problems with it.
First, as NoTrueFlags points out, Bentley was living in Connecticut at the time, not New York.
Second, I just don't see an intelligent, sophisticated person like Bentley making the call to someone who might be related to Tippit, living in a completely different part of the U.S. (Rather than calling authorities in Dallas, or Washington DC, or even in her own city, New York.)
Third, I find it a little difficult to believe she would use a fake accent.
And fourth, how would Bentley know that the orphan she'd seen several years earlier was the same person as Oswald?
What I'm inclined to believe is that there was a woman who was charged with taking care of the orphan boy. And that she did have an accent. And that she called Tippit because she was unsophisticated. Finally, that she recognized Oswald as the orphan she had taken care of simply because they looked the same.
When I was in my twenties, I bumped into a guy at Radio Shack who recognized me and remembered my first name. Yet he hadn't seen me since third grade. Point is, the looks of some people don't change a lot from childhood to adulthood.