The highly-rated defender's performances caught the eye last season as Coventry finished runners-up to Spurs in the FA Women's Premier League. Spurs went on to win the national play-off against Blackburn to take their place in the Women's Super League next season.
It's the team's second signing in as many days after announcing the capture of top WSL2 striker Sarah Wiltshire.
"Ashleigh is certainly one of the best defenders we faced in the league last season," said manager Karen Hills.
"She's versatile, strong and attack-minded, she's alwways looking to push forward but she's a great defender as well, so she's really suited to our style of play."
Below: Ashleigh with Karen
Ashleigh added: "Spurs were outstanding in winning the league last season, unbeaten for so long and what impressed me was they always found a way to win.
"It's that little extra - perhaps an extra training session - that means they were able to do that.
"When I first came down to speak with Karen I came to the training centre and it's out-of-this-world. We're so lucky to be able to train here.
"This is a new adventure for me as well, I haven't played in the WSL myself, just the Premier League and I'm really looking forward to next season. It's where I want to be.
"We've such a great squad here, the players made me feel so welcome and I'm really excited for the new season."