It is no more or less "hypocritical" for a politician of any party to send his or her child to a commercial school than it is for a politician of any other party to do so. At least Labour politicians ever use the schools for which they legislate, unlike most Lib Dems or practically all Conservatives.
As Harold Wilson made manifest while both Prime Minister and a parent, there has never been any Labour Party policy to abolish these strange institutions, which sell themselves as especially adept at putting pupils through an examination system which is largely rubbish anyway, and which frequently embody the views that adolescence ought to be lived out in single-sex residential environments while the relationship between parents and children ought to be strictly financial and nothing more.
Meaning that Diane Abbott was no more or less a hypocrite than any Conservative or Liberal Democrat, including Nick Clegg. She certainly acquitted herself better than Tony Blair or Harriet Harman, who did in fact send their children to schools that it was then, although mysteriously not for very much longer, the Labour Party policy to abolish.