Board Thread:Metal Gear Solid V/@comment-3131736-20151003235805/@comment-8839944-20151004001140

NO. You can not get her back after finishing "A Quiet Exit". What they say is true. You need to restart it and equip the Butterfly Emblem to keep her as a buddy.

What triggers her disappearance? You have to have reached that stage of the game where a new parasite stain infects the people on the Quarintine platform. She'll disappear after that, I believe. You have to have 100% buddy rating with her, though, to trigger it.

I don't remember the exact mission that she dissapears in.