Nikita Parris continued her excellent scoring form, coming off the bench to inspire the Blues to victory, while Pauline Bremer scored her first goal since returning from her lengthy injury lay-off.
The first chance of the game fell to Watford’s Helen Ward just two minutes in, but the forward’s shot was comfortably dealt with by Karen Bardsley.
Heeding the warning, City kicked into gear and Mel Lawley struck a long range effort just over the bar. That effort was quickly followed up by another from Keira Walsh, who was denied well by the fingertips of Watford keeper Weronika Baranowska.
WATCH: Inside City | Episode 327
Half-way through the first-half, a superb counter-attack almost gave the Blues the lead as a cross into the box from Lauren Hemp fell to Jess Park, forcing Baranowska into another fingertip save.
City thought we had finally managed to break the deadlock when Bremer headed the ball into the top right-hand corner of the goal just five minutes before the break, only for the forward to be flagged offside.
Nick Cushing’s side continued the second-half where we had left off. An early chance after the break fell once again to Park, who had beaten Baranowska but was denied by a goal-line clearance from Watford’s Emily Hill.
The Blues finally made the pressure count in the 62nd minute, as substitute Parris opened the scoring by coolly slotting the ball into the far corner.
But City didn’t stop there. Just seven minutes later, Parris bagged her second goal of the game - again guiding the ball into the bottom right-hand corner after latching onto Park’s pass.
The Watford 'keeper continued to be called into action, making a fine stop to prevent Tessa Wullaert from adding her name to the scoresheet minutes later.
The chances kept coming for City and Parris would have completed her hat-trick if it wasn’t for Baranowska, who made three brilliant consecutive one-on-one saves.
There would be another chance for City’s number 17 to clinch her hat-trick but the forward opted to unselfishly pass, squaring the ball inside the box to Bremer, whose strike swerved just the wrong side of the post.
However, it was soon made three and it was City’s number 9 Bremer, who scored it! Finding acres of space inside the box, the striker slotted past Baranowska to put the game to bed.
How we lined up
Walsh, Georgia Stanway, Lawley and Park made up the midfield with Hemp and Bremer up top.
The draw will take place on Monday 4 February at 6:30pm, live on BBC News' Sportsday.
City return to action on Wednesday 6 February as they take on Chelsea in the FA WSL Cup semi-final, with kick-off at 7:30pm GMT.