The actress, best known for playing Walford's Sam Mitchell, will feature in an upcoming storyline with the Channel 4 soap's McQueen family.
Westbrook's character Trudy will be seen on screen from February when she hires cash-strapped Jacqui (Claire Cooper) and Theresa (Jorgie Porter) as cleaners.
While exact details of the subsequent story have yet to be disclosed, viewers will see that Trudy shares a history with Jacqui as the characters were previously in prison together.
Westbrook is already friends with Hollyoaks co-star Kieron Richardson (Ste Hay) after they both competed on the 2010 series of ITV1's Dancing on Ice.
Hollyoaks airs weeknights on Channel 4, with first look screenings on E4. Get the Inside Soap magazine on your iPhone or iPad