Moaning Myrtle was crying noisily in her cubicle, but they were ignoring her, and she them.
I guess it just means she was ignoring them too. But I have never seen this kind of structure before. Is it common? Any other examples for this kind of structure? What does it truly mean?
— From Harry Potter.
Best Answer
Yes, you're exactly right about the meaning. This is an example of a kind of ellipsis, or leaving words out. It's commonly used for words that would repeat exactly in a single sentence, so
would usually omit all but the first "I ate":
Note that sometimes we also leave out the articles, even though they aren't exactly the same because of the a/an distinction.
In this case, the "expanded" version of the sentence would be
In this case the verb conjugation has changed because the subject of the two clauses is different. This is a little less common than omission when the subject of the clauses is the same, but it's not ungrammatical. One example is the stereotypical formal dialogue between lovers:
B leaves out the verb "love" because A already said it. As you guessed, this is just a different way to say "I love you, too": by leaving out the verb, B acknowledges that it was just said by A.1
As an American, this particular kind of ellipsis feels a bit old-fashioned or British to me, so I'm not surprised that it's in a work by a British author. The linked article is from "Grammar and Style in British English", which offers another example where the subject changes:
1 The couple is so in love, A can finish B's sentences before B even says them!