Elsa was Toulon's main reason for using his puppets for revenge against the Nazis; When Andre came across jars full of leeches he was inspired to get this revenge.
After reanimating Elsa in her doll and seeing what pain and shock she was in, Toulon pushed a leech into her mouth, transforming her into the seductive hag-like puppet she is usually seen as (Whether this is the fault of the leech, or whether this is what Elsa truly was like on the inside is unknown).
As a puppet, Leech Woman is usually calm and only attacks targets that are already helpless, many times not fighting at all.
Leech Woman can vomit poisonous leeches from her mouth. These leeches seem to be either more powerful than normal leeches, they're simply magic or poisonous, as they can kill humans and they die once they've killed them, similiar to a face hugger
- Killer leeches with venom
In Puppet Master II, Leech Woman was thrown into a fire by one of her victims, named Martha, supposedly killing her for good (Supposing Curse of the Puppet Master is not canon, or indeed comes before part 2).
Torch and Blade avenged her death. Her death is met with regret but not real grief from a zombified Andre Toulon (Who was in fact at the time trying to resurrect Elsa through different methods), which raises some questions as to his mental state upon his resurrection.