Sorry to be that guy but the story doesn't really matter. It's obvious that she was created specifically for DOAX3 but then TN decided to have her as DLC to sell more copies of Last Round. That's why she's a copy character, it was easier to just paste everyone else's moves on her rather than make something new like with Marie Rose.
This is why I think there's no coherence to how she fights because she doesn't seem to follow any of the regular styles DOA is know for. She can be quicker than Christie or slower than Leon depending on how you play her. Still, I like her a lot but don't need (or want) to know who the fuck she is in the story.