This paper draws on materialist feminist theories to rethink relationships between girls' bodies and agency. New feminist onto-epistemologies redefine agency as "becomings" that dynamically emerge through assemblages comprising moving bodies, material, mechanical, organic, virtual, affective and less-than-conscious elements. Vignettes from a multi-modal, ethnographic study conducted over three years are used to demonstrate how place influenced young teen girls' body-movement repertoires. The place was a former coal-mining locale with a proud tradition of masculine, working-class labour. The vignettes focus on corporeality and demonstrate wide variations and fluctuations in girls' experiences of agency, which we theorise through the Deleuzeo-Guatarrian concept of "becoming". We discuss how material feminism(s) helps us to understand girls' becomings as emergent within assemblages that carry legacies of the past. Some girls experienced becomings that could not easily be spoken about yet which allowed them to imagine expansive futures while others felt unable to move on in life.