Elves and half-elves, like other humanoids, get frail as they get older. The question would be "is she still able to still fight?". They're putting her in the game, so I'm guessing she's old...but not too old for zany antics.

Species that get stronger with age are most creatures that live in the outer planes (they're basically immortal). Dragons (not actually immortal), and probably a few other things.

Edit: typo

As a fighter she might be less impressive, but she is also a Druid, and she has all the uber level and equipment she collected during traveling with Gorions ward.