If feathers are loose and she is moulting then she will pull them out.
Which feathers is she concentrating on??? If round her tail/bum then could very likely be lice... a dusting of louse powder should do the trick. I dust mine every month so they rarely have lice now.
Problem with lice is if you dont catch them early they can be a bugger to get rid of properly. The lice lay eggs round teh bum - looks like white dried poo usually so its hard to tell but you must get this white stuff off - pull the feathers or cut them off - if this is the problem of course.