I mean. You can have a character have a widow history without them directly replacing Romanoff. If you watched Black Widow you'd know there's like 20 of them. Idk what they're trying to do introducing another widow but there's not really anything that suggests she's a Natasha replacement.

Pretty sure it was confirmed by Kevin Feige and literally everybody that saw Doctor Strange 2 that she didn't die at the end. There was an explosion of red magic right as the place came down on her, and that was intentional. They just barely scratched the surface with Scarlet Witch, of course they're bringing her back.

There's nothing to "disprove", it's a joke. And the joke refers to people how many Blades there have been, in movies, clearly, as there have been multiple Blades in animation. Ali's Blade has been officially dropped, and with the joke being in reference to movies, no it hasn't been "disproven". Not yet anyway.