。
She slowly walked away from me.
Literal
She [topic-は] me [from-から] slowly walking went-away.
歩いて去る ('walked away,' literally 'walk-and-leave') is a standard manner-of-motion construction in Japanese: a verb of manner (歩いて 'walking') chains via te-form into a verb of departure (去る 'leave / go away'). Adding ~ていく ('move away from speaker') gives去っていきました — emphasizing the trajectory away from the speaker's vantage. ゆっくり ('slowly') describes the pace, lending a wistful, almost cinematic feel. The polite ~ました frames this as a recounted past observation.