Wassell debuted for the Scottish national team in 2014 in the opening Six Nations match against Ireland and played in every subsequent national match until April 2022, a wrist injury calling a premature end to a record-shattering streak of 54 consecutive international appearances. Wassell played a key role in the decisive 59–3 victory against Columbia in February 2022, booking Scotland's place in the Women's Rugby World Cup for the first time since 2010. Despite scoring in the Women's Six Nations 2021 match against Italy, the team were defeated, as the visiting side triumphed with a 41–20 win. She was a member of Scotland Women U19 7s squad in 2013, and also played in the Scotland U20 side, which beat Finland earlier that year. In the 2017 Women's
Six Nations, Scotland's defeat of Wales proved a career highlight for Wassell. She was named in the Scottish side for the
2025 Women's Rugby World Cup in
England. == Personal life ==