If her upper beak is too long, it could certainly interfere with being able to eat. I have not had this problem with any of my chickens; however, I do have an Eclectus parrot, whose beak we have had to trim . The first time we took her to an avian vet who charged $20 just for the beak trim, and he put her to sleep to do that, plus $80 more for the exam (ouch) and the 2nd time, we took her to a general vet who charged only $7.50, and when I watched him do it, he used a little pair of scissors for trimming dog toenails, and I figured I could do that, so I bought myself a pair of the scissors, and the last time, we just did it ourselves. Just have to be careful not to cut too much off, or it could bleed (just like cutting off too much claw). I wonder if something else may be going on, since she does not want to come out...