The 'Young' singer and X Factor judge donned a simple white dress to promote the book at the Kent mall yesterday (September 26).
A sizeable group of supporters holding banners waited patiently for the chance to meet and be pictured with the former N-Dubz star.
Contostavlos will also hold a signing at a WH Smith in Milton Keynes this evening (September 7).
In Honest: My Story So Far, Contostavlos shares her regret at losing her virginity at 14 and opens up about being sexually assaulted as a teenager.
She also addresses her recent sex tape scandal, writing: "My job as a judge on The X Factor was to smile and be smart and funny. But underneath I was petrified of being made to look like a slapper in front of the nation.
"I went completely numb [after the tape leaked]. The next day it hit me like a train. I couldn't stop crying. It was like my whole world was ending. I had terrible heart palpitations and despair and panic overwhelmed me."
Contostavlos has confirmed that N-Dubz plan to reunite in 2013.