The teenager had only been on the pitch seven minutes when she opened the scoring with a low angled finish in the second half before Neve Herron doubled the lead moments later.
Jenna Legg almost sparked a late comeback when she headed in from close range, but the Black Cats held on to record their second league win in a row.
Head coach Mel Reay named the same starting XI who hammered Sheffield United 4-1 in their previous game, with Louise Griffiths and Keira Ramshaw returning to the squad following suspension and illness respectively.
Sunderland AFC transfer gossip: Aiden McGeady urges Celtic's James McCarthy to join Alex Neil on Wearside
Transfer news: Leeds United set to sign Sunderland 'target' with ex-Wigan Athletic and Everton man set for move
The stunning £975m market values of Championship squads this season and where Sunderland rank alongside Sheffield United, Middlesbrough and co
Sunderland AFC transfer news: Cats miss out on £2.5m 'target' as ex-defender makes Switzerland move
Sunderland target left out of Premier League squad amidst transfer and contract speculation
But Reay was forced into an early change when forward Emily Scarr had to come off after a sickening clash of heads in the opening minutes which required lengthy treatment on the pitch.
Sunderland weren’t troubled too much by the disruption with England youngster Jessica Brown coming on as a like for like replacement, and had the first chance of the game when Abbey Joice drove through midfield and played in Maria Farrugia whose left-footed strike was well held by Georgie Ferguson.
Aside from Holly Manders’ 25-yard freekick which flew over the bar, neither side created much in the way of chances in an even first half. It was a different story after the break as first Neve Herron and then Corrine Henson tested goalkeepers Ferguson and Claudia Moan.
On the hour, Reay introduced Watson and Griffiths in place of Brown – who seemed to have rolled her ankle – and Holly Manders, with the former making an almost instant impact.
Farrugia slipped away from Francesca Ali and unleashed a dipping, swerving shot which was parried into the path of Watson who hit the ball first time across goal, underneath Ferguson and into the bottom corner.
The Golden Girls barely had time to react when Herron made it two. Emma Kelly sung in a deep corner and the midfielder rose highest in the box and her looping header crept in under the bar despite Rosie Kmita’s desperate attempt to keep it out.
Herron almost claimed her second with another header from a Kelly set-piece but this time her effort was blocked by Ferguson.
Sunderland have found their scoring touch recently and threatened to run riot again as Farrugia – who netted her first of the season a week ago – missed two opportunities to put the result beyond doubt. Creating space in the box, the Malta striker first put a left-foot strike inches wide of the upright and then saw a certain goal headed off the line.
The visitors gave themselves a glimmer of hope in the 93rd minute when Kmita’s corner was headed back across goal and Legg reacted first to nod past Moan, with Sunderland holding out until the final whistle in front of over 500 fans.
The Black Cats face Watford’s relegation rivals Coventry United at home on Sunday who are now just six points behind them with four games to play and the two sides facing each other on the final day.
Sunderland: Moan; Beer, McCatty, Towes, Mullen; Kelly © (McInnes 83’), Herron, Joice (Ramshaw 83’); Scarr (Brown 3’, Griffiths 68’), Farrugia (Blakey 83’), Manders (Watson 58’)
Subs: Cowling, Boyes.