This depends heavily on whether the two MCs were marooned with each other or not.
Adi, if alone, would survive just fine. She grew up in a subsistence/bartering society in the deep woods, so other than having to re-figure out what was okay to eat on the island, she'd set up a shelter, start a fire, and hunt/gather/fish for food. She'd be stuck there until another ship picked her up, but she'd be unlikely to die unless the island doesn't have enough resources to sustain a person.
Koreal, if alone, would grumble for a few seconds, cast a teleport spell, and be back in civilization moments later, because he's a wizard. Even if he couldn't do a teleport for whatever reason, he has plenty of ways to escape an island-- flight, breathing underwater, walking on water, cobbling together a raft and conjuring wind to carry him away... He wouldn't stay stuck, is what I'm saying.
If Adi and Koreal were stuck TOGETHER on an island, they'd probably view it as the opportunity to set up a private getaway. She'd get him to help her build a shelter (and probably a nicer one than she could manage alone, because magic), and they'd probably enjoy a tropical vacation alone with each other for a few days/weeks until Koreal got bored, and then they'd teleport (or whatever) back to civilization, leaving behind a way to return to the island if they wanted later. The shelter/resources they left behind may or may not be booby-trapped, however, just in case anyone ELSE stumbled on their private getaway.
