"Es war einmal eine alte Schweinemutter, die hatte drei kleine Schweinchen.".
By what grammatical rule causes die to mean 'her' in this sentence?
"Es war einmal eine alte Schweinemutter, die hatte drei kleine Schweinchen.".
By what grammatical rule causes die to mean 'her' in this sentence?
Es war einmal eine Schweinemutter, die hatte drei kleine Schweinchen.
Here, "die" is the relative pronoun in the subclause (after the comma) that relates to the subject of the main clause ("Schweinemutter").
It actually doesn't mean "her", but rather "who". It translates as
There once was a pig mother who had three little piglets.
German "die" can be a bit tricky, because it can be an article, a demonstrative, or a relative pronoun. Here, it's the latter.