Complex sentence: Elizabeth often cheated on her boyfriends and every time it was said how "uncharacteristic" it was of her--when in reality, given the number of times she cheated, it was totally in character.
Split into simpler sentences: Elizabeth often cheated on her boyfriends and every time it was said how "uncharacteristic" it was of her. When actually, given the number of times she cheated, it was totally in character.