The sound /er/ as in her can be spelled five different ways:
er, ir, ur, -or, and ear-.
In her excellent book on beginning reading instruction, The Writing Road to Reading, Romalda Spalding offers a useful memory device for learning the five spellings of /er/:
Her first nurse works early.
The words in this mnemonic are in the order of the most common spellings of /er/. When teaching the memory device to the beginning reader, point out that the spelling or stands for the /er/ sound only if it is preceded by the letter w, as in work.
The spelling ear for the sound /er/ will cause a few giggles at first, but the beginner will quickly learn that the pronunciation of the body part (ear) is an exception to the pronunciation of the spelling in words like early and earth.