Oh, Sonia Belmont. The unfortunate Vampire Slayer that came into the fray with a less than loved Castlevania game and retconned out of the timeline. Basically, in Konami's eyes, she doesn't exist. Headcanon reason? She encountered Mistress Death (yes, from Marvel) and was taken into some eternal damnation prison... forever a #DiD. Obviously, she was bound and gagged prior to said encounter; probably by some Belmont hating crowd that thinks the Belmonts are responsible for the uproar of the unholy supernatural like Dracula and the sort.
Until Next Time!