@Hiraelle She's never said to be dead, just "unmoving" after Trelawney saved her from Greyback and I don't think Rowling has said anything about her one way or the other either? I cant be too sure though... but in the books she's just "unmoving".
And as far as I'm concerned; what the actors/directors/producers of the movies say happened is irrelevant. Like you said, they're not canon.
The last we see is actually "feebly stirring", which I'd take for suggesting that she had a chance of recovery. Although with a horde of giant spiders and curses flying everywhere that could be unlikely...
https://cybre.space/media/C1o60Cph61nWqGKW8mM
Pottermore isn't canon per se, but it used to say "presumed dead, 2nd May 1998" (https://web.archive.org/web/20150922164556/https://www.pottermore.com/explore-the-story/lavender-brown) and now doesn't.
@Alxndr_18 @notgomen I'm gonna headcanon that she survived
@notgomen yeah, pretty much what I thought too, thanks