Is this another sentence fragment or is it the phrase you would use if you wanted to say, e.g., "her hearing was bad"?
It could be that which would be "Mae ei chlywed hi'n ddrwg." or it can be used when as a verb e.g "Wnaethoch chi ei chlywed hi?" (Lit: Did you her hear? or "Did you hear her?"). Though this probably is a fragment sentence that has been deleted since it matches with many other fragments that have already been deleted.