In the end of Deadpool 2, Deadpool receives the time machine of Cable, modified to be used multiple times. Then he actually saves Vanessa's life with it, among other things.
Did he actually do this? Does that mean she is still alive and will participate in Deadpool 3? Or is it just some post credits fun?
That post-credit scene is CANON as the writers said during their reddit AMA:
Q: IS THE AFTER CREDIT SCENE CANON??? Please tell me I’m dying to know!
A: Yes, the after credit scene is CANON! Don't expect that device to stick around beyond this movie, though!
So yes, Vanessa is alive and in a universe that is beautiful and just, Green Lantern movie and mouth-shut-pool does not exist...