。
She kept dancing the whole time at the party.
Literal
She [topic-は] party [genitive-の] interval [throughout-ずっと] danced-keep.
間ずっと is a temporal phrase meaning 'all the way through, the entire time' — 間 ('interval, duration') intensified by ずっと ('continuously, all along'). Combined with ~続ける ('keep doing X'), it stacks two markers of unbroken continuation: the temporal frame and the verbal aspect. ずっと on its own is one of the most useful adverbs in Japanese, covering durations, distances, and even intensity ('much more,' as in ずっと大きい).