She scored both goals as the Reds defeated Oldham Curzon 2-1 at Poulton Victoria yesterday.
After going 1-0 down to a spirited Oldham side, Foster drew her team level when she ran onto a pass from the left and drilled it into the bottom corner of the net from outside the area.
For her next she beat two defenders in the box before coolly slotting the ball home.
Manager John Williams said he believes his squad won the title in August last year.
"We played our first game on August 17 and set our stall out in that really, when we beat Sunderland 5-1," he added.
"The girls have worked hard all season to keep that standard and really deserve their success, even if this was a scrappy game. Oldham deserved a point really, but the strength in our team won the day and Cheryl took her goals well."
The victory means Liver-pool now have 41 points and while Sunderland are mathematically able to catch them, the Reds' vastly superior goal difference of plus 32 to the Black Cats' plus six will see them over the line.
Williams added: "The Sunderland manager brought a bottle of champagne into the dressing room after the game to say well done, but the girls are keeping it on ice for now because they want to win their final three games, finish with 50 points, and go the entire season undefeated.
"They are delighted though to have won the title - especially Gill Hart and Jade Thomas who were here when we were relegated - and it means a lot to me too because it has taken a lot of hard work to reach this point.
"It is a tribute to the entire staff and players and to the support we have had from Liverpool FC."
Williams now hopes to play a game at Anfield before the end of the season.
"The FA have said they will present us with the trophy at Anfield at half-time or before a game, so if we could play there too it would be amazing," he said.
