。
She spoke with gestures.
Literal
She [topic-は] gestures [object-を] mixing-in [then-て] talk [object-を] did.
身振りを交えて describes the manner of speaking — she incorporated physical gestures as she talked. The te-form of 交える presents gesturing as an accompanying method rather than foregrounding simultaneity the way ながら would. 話をする ('to give a talk, to speak') uses を to frame speaking as a more deliberate activity than simple 話す.