Trollge Gf is a form of Girlfriend and is the opponent of Thanatophobia. During the events of Story Mode, Girlfriend is brainwashed into a Trollge-like entity by Legion. While in his control, she gains a new form that is several times taller than her original size, with her face turning white and her entire body, including her heals, being colored black. Gf also gains yellow, normally pupil-less eyes, sharp teeth, and long claws for fingers. This form serves as Boyfriend's opponent during Thanatophobia and My Dear Love. Halfway into Thanatophobia, Gf starts to break down, trying to get herself out of Legions control. In My Dear Love, Gf is sitting on the ground, almost out of Legions control and Bf has to sing her out of it.

More facts here : https://fridaynightfunking.fandom.com/wiki/The_Trollge_Files