She is ageless. She and all other Amazons were blessed by the Greek goddesses so that they will never grow old. In post-Crisis this is true whether she leaves the island or not, and only if the goddesses choose to withdraw this blessing from her will it be "negated," or if someone uses magic -- powerful magic -- to dispel it.
However, she can still die by natural causes such as, well, someone else killing her. If Grundy snaps her neck, she's dead. If Darkseid hits her with his omega beams, she's toast. The end.
With all that said, however...she is the most favored champion of the Olympian gods. They have the power to resurrect her if they want to, and that's exactly what they did when they made her a goddess. But the first time they made her a goddess didn't end up so good since she kept interfering with the mortal world -- which is why they eventually took away her godhood -- and so the chances of them ever doing that again is slim to none. And not to mention, the Olympian gods aren't even around right now, since they've left this plane of reality. So basically, if she dies then she's dead...no "loopholes."