Having progressed through the youth system at Nottingham Forest Ladies, Bradley-Auckland joined Leeds United Ladies in 2006 for a four-year spell.
She then moved to Lincoln Ladies and Notts County Ladies before switching to the Belles in 2017 and helping them win the WSL2 title last season.
"This is a great move for me and I'm really excited for the new season," she said.
"Liverpool is a fantastic football club with real ambitions to be challenging for trophies again so this was an easy decision to make.
"The opportunity to work alongside Neil [Redfearn] again was also a real pull as I feel as though he helped to develop my game to the next level last season.