What should a 5'4" 14 year old girl weigh?

That is indeed a little too low for your age. Try eating some more and taking protein shakes. Definitely visit a doctor.

One gauge is your skeleton size: when I was a girl, the general rule was to allow 105 lbs for the first 5feet (if your bones are small), and 5 lbs for each additional inch of height; or 110 + for a medium frame, or 115 + for large bones.

But, know what? You're still growing! I think you'll grow into your height if you feel good and have energy and a good appetite. Young people's skeletons grow faster than the rest of their bodies, and the reason teens are usually depicted as having ravenous appetites is their bodies are trying to keep up with their bone growth.

Also, some people are just made to be slender. If that's true for you, you're society's ideal and many women will envy you!

85 Ibs

I'm sure you're fine :3 I'm 15 and I'm 5'4" and 90 pounds. Trust me you have nothing to worry about okay :3 When I was 14 I weighed the exact same :3

You're very underweight. See a doctor.