Mary, there are many different things that can cause feather
plucking, from medical issues to boredom to neuroses. I would
start with a vet check up to make sure she has no medical
issues going on. Metal toxicity (zinc) for example can cause
feather plucking. If she is chewing on toys or chains that may
contain metals consider removing them from her cage. Stainless
steel is best.
Also, is she getting regular misting or showering. This is
very important. If not, use just plain water and mist over her
and let the mist gently fall onto her feathers. OR you could
try taking her in the shower with you, make sure the water is
deflected so it doesn't hit her directly. She may be scared at
first but should start to love showers.
Diet is also important as a poster previously posted.
If all checks out, this may be a phase but keep a close eye on
her as it can become chronic. I am attaching links to some
good information on feather plucking. Most of this information
in these articles is for owner's whose bird's feather pulling
has become serious, which is definitely not what you are
dealing with now. But it will give you some insight. My
umbrella 'too has had brief periods of pulling feathers on the
fronts of her legs, but always lets the feathers grow back and
hasn't done it in a couple of years.
Good luck with your 'too.