My sister has inflammation of cornea. What should I tell her?

See an eye doctor. The cornea can swell as a result of several conditions, but true inflammation is much less common and is often a result of infection. Regradless of the cause, any decreased vision from corneal swelling should be evaluated by an eye doctor. There are usually very good treatment options available.
Obtain diagnosis. Corneal inflammation is only a description. Corneal evaluation by an ophthalmologist is essential. This will likely produce a diagnosis, which will likely lead to suggestions of treatment options, need for further local ocular and or systemic testing and yet additional possible treatment options and prognosis.