Beth England bagged a brace to keep Gordon Stainforth’s side in the hunt for promotion from the FAWSL2.
The Doncaster midfielder struck a second half double in the space of two minutes as the Belles rallied to their tenth win of the season.
Courtney Sweetman-Kirk got the ball rolling as she drilled an effort into the bottom corner for an 11th minute lead.
Doncaster were in control for the opening half hour as Millie Bright and Tori Williams looked bright in possession.
However, Millwall got themselves back on level terms in the 36th minute when the Belles failed to deal with a searching ball from former Doncaster player Lillie Billson. She found Cherelle Albert who coolly guided the ball past a stranded Nicola Hobbs for 1-1.
Albert nearly added a second when she capitalised on a defensive error, but her powerful shot was smartly saved by Hobbs.
England was first to have a shot on goal after the restart, which Quantrill saved, before having another long range effort cannon back off the bar.
The Belles rallied as Sweetman-Kirk had two chances saved well by Quantrill who was proving a thorn in Doncaster’s side.
Jess Sigsworth, who replaced Hope Knight in the second half, later curled a chance towards Quantrill’s near-post but the Millwall number one denied the Auckley forward.
However, Doncaster’s pressure soon told as England rifled in her tenth of the season from close range in the 54th minute.
The forward-thinking midfielder was on hand to slot the ball home just two minutes later for her brace and her 12th goal of the season in all competitions.
Tori Williams should have put the game beyond doubt in the 67th minute but failed to get the desired purchase after latching onto Lyndsey Cunningham’s pinpoint delivery.
Sweetman-Kirk was later denied her second and Sigsworth sent a bullet header the wrong side of the post before substitute Reanne Thomas fired home in injury time, powering Doncaster towards a vital victory - reducing the gap at the top of the table to five points.
FAWSL2 leaders Sunderland face Yeovil Town on Sunday with the Lady Black Cats looking to restore their eight point advantage.
Belles: 1 Hobbs, 2 Cunningham, 4 Little (c), 6 Lipka, 8 Smith, 9 Sweetman-Kirk, 11 England, 24 Knight, 15 Williams, 20 Roberts, 10 Bright. Subs: 31 Govier, 5 Sigsworth, 13 Stamp, 16 Mills, 12 Thomas, 23 Cresswell.
Millwall: 1 Quantrill, 22 Mackie, 17 Fisk, 14 Davies, 3 Strugnell (c), 30 Sherwood, 15 Billson, 28 Lamb, 9 Maple, 8 Agg, 11 Albert. Subs: 32 Cowan, 9 Stenning, 19 Ali.