It feels like Qiyana is a mishmash of a laner and jungler.
How she obtain the elements she desires and terrain ulti does feel more suited to use inside the jungle, while her assassin-like style, like the stealth and the extra damage from the elements from walls belong to a laner (because who is going to get water from top lane without leaving lane?) .
It’s hard for her to fit, because she doesn’t have any sort of sustain, both in mana and in health, and her assassination damage isn’t as damaging or scaling as hard as other assassins do.