Reading remain second in Women's Super League Two after inflicting a first defeat of the season on Everton on Saturday.
Goals from captain Lauren Bruton and winger Emma Follis gave the hosts victory, while Paige Williams scored Everton's consolation from the spot.
"We've had a rough patch and we've come back fighting now and everyone played amazing," Bruton said.
Reading travel to leaders Doncaster Rovers Belles on 16 May.
The Belles are three points clear at the top after beating London Bees 5-1 on Saturday.
Meanwhile, Millwall remain unbeaten in the league this season and moved up to fifth in the WSL 2 table thanks to a 2-2 draw at home to third-placed Yeovil Town.