Millwall took advantage of a slow start to take the lead after three minutes but the ladies responded and took a grip of the match.
Jenna Schillaci levelled with a fine volley from the edge of the area on 35 minutes and Kim Lane struck the post just before the break.
The second half was one-way traffic and after a couple of near misses, Natalie Grafton netted what turned out to be the winner from a corner on 70 minutes.
Andra Marcoci and Katie O'Leary also went close as the ladies made it six wins in seven in pre-season.
The team face a Barnet Development Squad on Sunday, their final match before they kick-off their FA Women's Premier League South campaign at Chesham on Sunday week, September 1.
Spurs Ladies v Millwall: Jo Ayre, Derrie O'Halloran, Kim Lane, Jo Woodgate, Natalie Grafton, Jenna Schillaci, Fran Gamble, Mollie Kmita, Roise Kmita, Bianca Baptiste, Andra Marcoci, Robyn Downie, Joran Arnout, Katie O'Leary.