How's it tough to work her into the story? Just have an incident happen where she is or have her go into a situation because Chris and the BSAA are too busy elsewhere and she feels that something should be looked into.
Before you die you see the Tails Doll---Backdrop Observer of the Metroid: Other M board Apparently Edward: Wise Old Sage of Korodai
Seriously I know Jill was in 5, but not counting DLC, she wasn't a main playable character. And Revelations had both Jill and Chris has main playable characters right? I really no nothing about Revelations since I can't play it :v