I was just thinking if 
all of a sudden loses her powers or if the aspect inside her body decides to leave (if thats even possible)
does she stay normal but she starts to age or does she turn into dust because of how long she been alive for?
I'd imagine that, even if the Aspect of Twilight left Zoe for whatever reason, her body would be so suffused with it's power that she'd still be able to do what she does now, though to a greatly diminished capacity. She probably won't be warping around the cosmos or conjuring town destroying meteors or anything, but her portal magic and ability to conjure small celestial objects would still remain.
There's also the potential that when the Aspects have no need for their mortal avatars to guard Runeterra, or any world, they'll bring them in to Targon Prime as a reward for their service; an ascension in to some heavenly, cosmic realm doesn't sound too bad really. Atreus was taken there and came back imbued with Pantheon, so we know that, though thoroughly changed by the experienced, humans can go to Targon Prime.
Considering the Aspect is now Merged with Zoe according to her story my guess is, it will leave a somewhat empty shell,with maybe some traces of its power. just like Sharjo said. but that would be the case if they are forcefully seperated. unless aspect of twilight is a jerk and just leave Zoe after it's done with her.
This reminds me of another question i had about aspects, and Aurelion sol, what happens if Void manage to corrupt them as well? is that even possible?
oh hell... i just thought: Void Touched skinline for Sol and aspects! D:
Zoe doesnt have the aspect inside her, only its powers. As for an answer, no clue.
Well there is freezing the aging process
and then their is extending live beyond it's natural limit.
