Mitchell becomes City's third loss in just over six months to professional football abroad, with Jane Ross and Lisa Evans also departing.
Similar to both, the 20-year-old has spent her entire senior career with City, making her first-team debut at 15.
On leaving the club, Mitchell said: "I want to thank everyone at the club for their support over the last five years.
"I genuinely would not be where I am with my football today if it wasn't for this club."




