Star Wars: Every Jedi Who Turned To The Dark Side

Trilla Suduri was a force-sensitive with a brilliant intellect who trained under the Jedi Knight, Cere Junda. After the fall of the Republic, Cere and Trilla attempted to hide a group of younglings from Imperial forces. In the aftermath of Order 66, Cere and Trilla were discovered by an Imperial patrol. Cere decided the two would split up, and that she would attempt to lead the Imperials away from Trilla and the younglings. Trilla begged her Master to stay with the group, but Cere refused.

Cere succeeded in distracting the Imperials, but she failed in eluding them and was captured. Cere was taken to the group of Jedi hunters known as the Inquisitors and was subjected to intense torture, and eventually betrayed the location of her Padawan, Trilla.

When the Empire captured Trilla, they subjected her to the same torture as her Master, and eventually, Trilla gave in to the dark side of the Force. Trilla would transform into a lethal Jedi hunter known as the Second Sister. In fact, when her former Master, Cere, witnessed Trilla in an Imperial uniform, she totally lost it and killed everyone in the room, but Trilla, with the Force.

Trilla was abandoned, betrayed, tortured, and witnessed her own Master briefly turn to the dark side. You can't really blame her for turning. She never stood a chance.