Bloodborne modder Garden of Eyes usually only lets Soulsborne bosses take each other on in boss vs boss mod fights, but the excitement surrounding Resident Evil Village's tall lady of the hour, Lady Dimitrescu, seems to have inspired them to make an exception—after all Lady Maria and Lady Dimitrescu are both distinguished ladies with sharp arguments. They're also both vampires, which is probably the more obvious reason why she makes an appearance.
Lady D has got her own attack animations, slicing and dicing Maria with her sharp claws, plus a surprise transformation at the end. It's good stuff!
However, to keep things fair, Lady Dimitrescu has been shrunk to Maria's size, which of course eliminates one of the internet's favourite talking points, the fact that she's absolutely enormous. Otherwise, she's a good fit for Bloodborne's aesthetics, and as she's a little underused in her own game, fans would naturally try to make the most of her. If you type "Lady Dimitrescu" into Google, "Lady Dimitrescu model" is one of the highest-ranking search terms, which gives you a pretty good idea what else people are up to—they want to know who her face model is, of course.
The comments to the video are predominantly horny, though. Of course they are.