Anaphora is the name for the relationship between she and Mary in—
Mary looked out of the window. The sky looked threatening, so she decided to take an umbrella.
What the two highlighted words share is the fact that they both refer to the same person – they have the same reference. The word she refers back to the word Mary without repeating the name. This ‘reference back’ is called anaphora. Successful writers keep track of the various people and things that they mention by building a reference chain by means of anaphoric devices such as pronouns. KS3 writers sometimes fail to make these links clear, thus spoiling the coherence of their writing.