Honestly, I see two distinct camps for elven princesses in epic fantasy. There's the classic 'living artifact' type, born with a magical connection to her realm's forests, waters, or moons. Her power is often a subtle, ambient authority—animals listen, plants grow faster, and ancient spirits recognize her bloodline. It's less about fireballs and more about harmony and natural order.
Then you've got the more modern, action-oriented version, where she's a combat prodigy. Think flawless archery blended with nature magic, like summoning vines to entangle foes or calling a storm with a song. Her defining trait is often the weight of legacy; she's a repository of ancient lore and political power, making her a target and a linchpin. I find the former more interesting, though, when her 'power' is her unshakeable cultural influence, not just a magical skill set.