The problem with the Titanoboa is that it literally had no distinctive trait bar its size and this is a given even for a common snake if the user is someone as big as Black Maria. So Oda would need to get creative to distinguish the ancient model from Sandersonia's.
(Personally, if she's another dinosaur I may go for the Tyrannosaurus because of the well known specimen named Black Beauty; it would also be ironic that Black Maria, a name given to the Queen of Spades, ended up being a rex, which means "king").