To her credit, she does actually sing live. The Coca Cola concert she did in South America in 2011 had mostly live vocals as they had no lip track functionality.
It isn't. It doesn't involve ones personal life which is the lowest and where the biggest liars lie about. This is any different situation to Gaga's email, Janet''s Super Bowl, Christina her Gaga dissing backtrack, Beyonce's "inspirations" tales etc. It's to maintain ones public reputation.