She winds up jumping into the fight with Iron Man, Doctor Strange, Spider-Man, Star-Lord, Drax, and Mantis, but that just leaves her on the losing team.
In retrospect, though, their choice is interesting when you consider the size of Nebula’s role in Avengers: Infinity War.
All things considered, she doesn’t actually have much to do in the monster blockbuster.
She first appears when Gamora is brought in to witness her torture, and that sequence is followed later by a brief scene where she escapes bondage and kills the minion guarding her.