Is she even supposed to have appeared? I haven't read all issues but for example, at the end of the last one on the page featuring the coming Young Animal titles there's written: "[...] Plus the introduction of our newest character and title: Eternity Girl." so I'd personally assume she didn't yet. I have no clue what she's supposed to look like, though, so maybe she did and she needs to be added.
Oh, her, I've seen her in the main story in the last part of the event --> Doom Patrol/JLA Special Vol 1 1 You can add her.
For the back-up story, I think you can add it as a second story, I've seen that many times on this wikia.