Sarah was possibly wearing the Sculpt 7/8 Tight from Cotton On Body available here: https://cottonon.com/AU/sculpt-7%2F8-tight/663665.html

Cheaper duplicates: 
1. https://cottonon.com/AU/active-core-capri-tight/630469-99.html?dwvar_630469-99_color=630469-99&cgid=&originalPid=630469-99
2. https://cottonon.com/AU/dakota-detail-legging/241386-14.html?dwvar_241386-14_color=241386-14&cgid=womens-leggings&originalPid=241386-14#start=1