The Scotland international let fly with a dipping effort to put the Citizens back in front midway through the second-half of the FA Women’s Continental League Cup Group C clash at the Academy Stadium.
Former Blue Ellen White had put the hosts in front early in the second half only for Rachel Williams to get her fourth in three cup matches with an instinctive close-range finish.
The decider soon followed for a home side that had more of the ball throughout but Blues may feel hard done by not to have claimed a draw after creating some good openings on the break, particularly in the first-half.
Blues manager Marta Tejedor made one enforced change from the 2-0 Barclays Women’s Super League victory over Liverpool with captain Kerys Harrop suffering a muscle strain. Harriet Scott was drafted in at centre-half with Lucy Staniforth handed the captain’s armband.
Man City saw plenty of the ball throughout a cat-and-mouse first half but Blues generally kept them out of the 18-yard box other than a couple of five-minute spells.
Janine Beckie surged forward to clear the bar from the right corner of the 18-yard box before Pauline Bremer’s low cross-shot had to be parried away by Hannah Hampton but Blues weathered that storm and gradually began to fashion openings on the break.
Staniforth and Lucy Whipp combined to find Williams whose low shot was held by Ellie Roebuck to her right prior to the chance of the half.
It arrived 10 minutes before the interval with Chloe Arthur passing to Williams who released Brianna Visalli on the left of the box but the American could not make the most of her well-timed run and the shot was covered by Roebuck at the near post.
Bremer saw a looping header clear the bar for the Citizens from White’s drifting cross just before the break but the deadlock was broken six minutes into the second half when Lauren Hemp jetted past Sarah Mayling and cut back for White to rifle in off the underside of the crossbar at the near post.
A flurry of pressure followed with Adrienne Jordan and Mayling among those to make hurried blocks or clearances before Blues regained composure.
Having established a foothold in the game once more the leveller arrived in the 64th minute when Visalli steered towards the near post for Williams to stoop in and head home from close range.
The joy was short lived, though, as Weir unleashed a beast, striding inside to beat Hampton from 25 yards with a high, dipping effort that had the home crowd on their feet four minutes later.
Blues kept probing and had some decent moments on the edge of the box only to be snuffed out at the last.
Home substitute Jess Park might have wrapped it up late on with Hampton parrying to her right one-on-one but the final score ensured Blues, City and Manchester United – 3-0 winners at Everton – sit level on points and goal difference in the standings, although the Red Devils have a game in hand.
Man City: Roebuck, Beckie, Houghton (c), Bonner, Campbell (Stokes, 81), Scott, Weir, Stanway, Hemp, White (Geum-Min, 65), Bremer (Park, 78).
Unused subs: Toland, Wullaert, Fidalgo, Benameur (gk).
Goals: White 51, Weir 68.
Blues: Hampton, Mayling, Scott, Holloway, Jordan, Whipp, Arthur, Staniforth (c), Visalli, Williams (Walker, 89), Grant (Scofield, 77).
Unused subs: Brown, Brooks (gk).
Goal: Williams 64.
Referee: Elizabeth Simms.