。
She turned the pages excitedly.
Literal
She [topic-は] excited-being [while-ながら] page [object-を] turned.
~ながら links two simultaneous actions performed by the same subject — the excitement and the page-turning are happening together, not sequentially. The verb 興奮する ('to be excited') in its 連用形 興奮し attaches to ながら, giving 興奮しながら ('while excited'). めくる is the verb for flipping pages of a book or peeling away a top layer (めくる handles both the physical motion of turning a page and the metaphorical 'turning a new page'). The image is a reader gripped by what's on the next spread.