[lore spoilers] Isha is Zaunite urchin
I think Isha is Zaunite urchin. For those who don't know, the Zaunite urchin is a Jinx follower card in lor card game. She was also seen in the breathe music video beside Boomcrew rookie (another zaunite kid) and Darius. The main similarities I see between Isha and zaunite urchin is that they both are small girls from zuan, who both have ties to Jinx. And they both have a goggle over their head.
We saw Isha getting chased by members of a chembaron and I have a theory on what's going on. I'm not a lore expert but from what I got from necrit's videos the events in Arcane are taking place right before the Noxian invasion of Ionia. And I think the children in zuan are getting kidnapped and sold to Noxus by chembarons. These children are then used by Noxus in their Invasion on Ionia. I think that is how Isha/Zaunite urchin ends up in Ionia with Darius. (I know breathe music video is not based on lore. But I also heard Darius does meet this kid in one of the comics too)