The Doncaster-born forward has signed a new deal with the Belles after completing her studies at Sheffield Hallam University.
She is expected to feature against the Gunners on Saturday when Doncaster will be aiming to secure their first points of the new FAWSL1 season.
“I’m so excited to go full-time with the Belles,” Sigsworth told the club’s official website.
“It’s very special to do it for this club too because it’s my hometown team. I’m looking forward to pushing on now.
“The chance to go professional will help me massively in terms of technical work and tactically, and my fitness will continue to develop.
“I can’t wait to start training every day and improve as much as I can.”
Belles boss Glen Harris now hopes to nurture the ‘raw talent’ that has seen Sigsworth, from Auckley, represent England at Under-23 level.
“We’ve been desperate to do some prolonged work with Jess but it was important for her to finish her studies,” said Harris.
“Now that’s out of the way, she can relax, concentrate on football and, in her words, ‘smash it’ in training.
“Her raw talent can now be even further refined on a daily basis.
“You look at the likes of Kasia Lipka and Emily Simpkins since going full-time, the development of their technical skills has improved massively.
“So taking Jess’ raw athleticism and having the chance to improve her technically is only great news for the Belles.”
Belles have lost to Chelsea, Birmingham City and Manchester City since returning to FAWSL1.
Their tough re-introduction to life in the top flight continues with the visit of Arsenal, who won the FA Women’s Cup at Wembley on Saturday with a 1-0 win over Chelsea.