Wassell also played for Loughborough Lightning most recently in the league, alongside consistently representing her country over the past decade.
She made her debut in 2014 and set a new record by playing 54 consecutive international matches, a run that ended in 2022 because of injury.
Wassell said joining Trailfinders marked a “new chapter”.
“I’ve had a bit of a rough season to say the least, and I just cannot wait to get back,” she added.
“I want to push myself, be challenged with the competition at the club, but also enjoy it.”