Use a cat nail clipper. Get some syptic powder and only snip a tiny bit at a time. Wait a few days between tiny trims.
I have some parrots that need beak trims and so Im used to it, but if you go too fast it will bleed alot. So you want to be sure to go slow and use syptic powder or gel if it bleeds.. filing wont help much.
If she can eat OK, I wouldn't worry much about the beak. As long as she is getting food down, leave it until she has recovered.