I've been trying to remember what my mother said about when I was a kid (we're in Boston). I do recall she hated Joe Kennedy for it. Of course, she had no use even for rich people who kept their kids in boarding school and/or summer camp year round. I think her opinion was that Rosemary was just "boy crazy" and a bit wild.
An earlier article mentioned her recently-published diaries, showing she was cogent enough to write down her thoughts about tea parties and other events in her life. The article very pointedly said she was "mildly" retarded.