[mangoandmimi]

Is there anything physically wrong with her or just the behaviour change and apparently not eating? I assume she was tame beforehand. Their temperament doesn't tend to change like that just due to old age. Can you think of anything in her surroundings that has changed these few weeks - new pets, cage move, new setup/cage etc.
Would be a good idea to weigh her frequently to see if she is losing weight if you aren't already. As it may be that she is eating from her hoards and only taking a little extra. It wouldn't hurt to take her to the vets if you do think something could be wrong although if she looks ok in herself it may not be too helpful.