Just saw your plotting comment, I'd LOVE for them to fight each other! We can hash out how that'll go down since... it sounds like they'll both be pretty tough, but I'm hoping for Itachi to have a difficult time of it anyway. So maybe they fight, he's able to get a seal on her, they both come out of it with some of their own injuries/damage? He'll probably leave quickly to go lick his own wounds alone as soon as she's no longer possessed.

It'll be a great introduction to adult Re-L either way 8)