Did Birdie die? (Spoilers)

This might have been mentioned before, but I've just finished watching the movie.
And all we saw was Lena smack Birdie with the iron (I know she stabbed her as well, but she put up a good fight so it couldn't be that bad)

My guess is that she lived and once everything was out in the open and the police searched the house, she was arrested and more likely to be put in a straight jacket in hospital as appose to jail for the rest of her life.

Unless they wanted to make another movie and they could make out that she escaped and is following on what the parents did with a partner of her own.