Rather than simply being resurrected after her death in Infinity War (which is explained as something that cannot happen after being killed as a sacrifice for the Soul Stone), we saw a younger Gamora time travel from before the point where we first met her in Guardians of the Galaxy.
So, the new Gamora is actually the Gamora from nine years ago, a Gamora who never fell for Peter Quill.
What Happened To Gamora?
Of all the various developments that have changed things in the Marvel Cinematic Universe going forward, one of the more interesting was the way that Gamora was “brought back.”