。
She killed time by window-shopping around the stores.
Literal
She [topic-は] shops [object-を] aimlessly looking walked [and-て] time [object-を] killed.
ぶらぶら is a 擬態語 (state mimetic) for aimless, leisurely wandering — no particular destination, no urgency. Combined with 見て歩く ('walk around looking'), it creates a vivid picture of casual browsing. 時間をつぶす ('to kill time') is a colloquial expression. ぶらぶら can also describe things dangling or swaying, but the movement sense is more common.