PS Look outside the box,, children always say no or dont know. even when they do., I hear it all the time....
Yes I would be concerned and look at what is happening in her life as something is upsetting her, have there been any changes ,any new siblings, move of house of area ,divorce , any problems that may have upset her, has she plenty to do in her life sports ,Games and fun, is Dad involved, if his is get him taking her out ,outside activities, focus on her positive side and praise her when she does something right .