Actually, it could have been a lot worse, she could have had a weapon. And, decided to take measures on for herself, because of you calling the police.
It could have cost you your life. The possibility remains, depending on what "he" thinks he is. If his ego gets the best of him, he'll be back to visit.
Especially, from the woman's reaction...tells me she is really used to it happening. Just because they were arrested, doesn't mean they will be prison. It's not guaranteed, even with your testimony. It really depends on their past history.
This might(or probably is) not their first encounter with police. Abusers are always being bothered by cops/police and the police really do not want to deal with it.
Just a thought.