The England international was a hit during her first spell at Blues, between 2011 – 2013, say birminghamcityladiesfc.co.uk.
She scored 14 goals in 14 games as Blues agonisingly missed out on the Women’s Super League title on the final day of the campaign.
She was voted 2011 Players’ Player of the Year at the FA Women’s Football Awards.
In 2012 she famously scored the stoppage-time equaliser in the Women’s FA Cup Final against Chelsea, which Blues won on penalties.
Williams later joined Chelsea, helping them to second in the league, before a January 2015 move to Notts.
Leicester-born Williams, 29, came through the ranks at her home-town club and also played for Doncaster Rovers Belles before joining Blues first time round.
She will link up again with, among others, Ellen White, who moved to Birmingham from Notts County ahead of the Spring Series.
Her addition will strengthen Skinner’s squad and boost Blues’ attacking options – and goalscoring threat.
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