What food did she switch from to? I know years ago when I switched to Solid Gold, my guys blew coat and one girl almost went bald. One they blew out the toxins (the almost bald girl had an allergy to preservatives that I didn't know about and she did have a thyroid condition), her coat came in beautiful.
So, in answer to your question: why she is blowing coat depends. Could be good news, could be not so good news.
Aren't you glad I answered?