apples from pears

While sitting on my desk sleepy and hopeless (a nap would be great to recover), I'm thinking of a friend's anecdote.

Her boyfriend was ill in bed, having a stomachache. She was at work. He was with his sister. The girlfriend knows about medicine, as both her parents are doctors. The sister doesn't know how to differentiate apples from pears. The girlfriend told the boyf to have some tea and some pills. The sister is in charge of nursing her brother.

Final act: my friend was angry, as the sister instead of giving a normal tea to the brother, prepared a medicine tea for colds...