Is it possible for Lucy to meet Aquarius again, or did she die/get sacrificed? Is it possible for Lucy to meet Aquarius again, or did she die/get sacrificed?

So is there only one key for each of the 13 gates? Or are there multiple keys?
Aquarius did not die, because when Lucy broke her Gold Key, she only became unable to leave the Spirit World and travel to Mage's World.

From Aquarius's article on Fairy Tail Wiki:


  Aquarius adds that breaking the key won't kill her, but will merely
  make her unable to leave the Spirit World.


And yes, there is only one Gold Key to each Zodiac Spirit. You can see all of them in this part of the Wiki.