She has been their " whipping boy" in the media for a long time. Maybe because she moved to the US it was easier to lay the blame at her door
True, the media are very tough on her and slate any success Nadine has had outside of Girls Aloud. Even though she moved, the girls could have still supported her. All of the girls loved it when Tweedy went to the states, but they never showed Nadine the same support.