Complex sentence: Ewen had not met the members of the Sugababes until two days before the video shoot for their single "About a Girl" in Los Angeles, having been flown there without being notified that she would be replacing Buchanan.
Split into simpler sentences: Ewen had not met the remaining members of the Sugababes until two days before the video shoot for their single "About a Girl" in Los Angeles. She had been flown there without being notified that she would be replacing Buchanan.