I just had a thoughts about Black Maria
1. If she will became a villain until the conclusion of Wano Arc, she might be a spy. I dont know who is she work for. It might be Blackbeard's spy or something.
2. If she will became our allies in the future story, she might working together with Hiyori.
And this is might be a point that Oda want to show to us if Hiyori is a daughter of Oden. She able to create some good strategies to take down Kaido and Orochi not by strength, but by brain.