I believe she went to the States originally to be with her boyfriend at the time and pursue business interests.
With all the negative press she got here I don't blame her for being wary about putting herself back in the spotlight here, especially with Cheryl's high profile. Both the press and some of Cheryl's most staunch fans ('soldiers') seem to take pleasure in perpetuating a Nadine v Cheryl 'feud'. Some appear to believe that if you like Cheryl you must dislike Nadine, and vice versa.
The worst person for this was the hideous Dan Wootton the former NOTW show business reporter, a more repugnant human being I've yet to encounter. He had an almost unhealthy fixation with Cheryl to the extent that anyone else who was seen as a threat to her career was subjected to hate filled bile from him, I think possibly because deep down he knew that Nadine had a far superior singing voice.
He seemed to take a very sick pleasure in watching Nadine's solo career fail to take off and at one point even tweeted that he'd seen one of CDs in a bargain bin somewhere. When the NOTW closed down and he found himself out of a job I took great pleasure in seeing him unemployed, a horrible spiteful little man. You reap what you sew and all that. Sadly this is what Nadine was dealing with from the UK press.
Cheryl has no singing ability whatsoever. Call My Name would have been an awesome dance tune if it had been performed by someone with a decent singing voice.