She battled against Emerald but lost, though she commented on how good Emerald was at battling.
Lucy is one of the Frontier Brains and runs the Battle Pike in Battle Frontier. In order to battle her, players have to complete the Battle Pike at least two times without fail (meaning that you have to clear 27 consecutive rooms) in order to meet her. If you defeat her, you can get the Silver Luck Symbol. In order to challenge her for the Gold Symbol, you have to clear the Battle Pike another eight consecutive times, or 10 times in total, (for a grand total of 140 rooms).
Lucy is the Frontier Brain of the Battle Pike. Lucy is found to have a secret crush on Brock during an episode of Ash challenging her (episode 435, Queen of Serpentine), and often blushes when Brock faces her or says something to her. It is said she has a penchant for Pokémon with squinty eyes (such as Snorlax, Abra, Makuhita, Skitty, Swinub, and a Cyndaquil, all of which have squinty eyes), and since Brock has squinty eyes, she likes him a lot too.
Lucy's Battle Sprite
Seviper is Lucy's main Pokémon. It was first seen battling Jessie's Seviper at beat it easily with pure brute force. It was later seen in her battle with Ash when it went up against Donphan and despite seeming to have the advantage Donphan managed to pull through with some thinking on Ash's part.
Milotic is an extremely powerful Pokémon in Lucy's possession. It defeated Donphan with one Hydro Pump. It then had the edge against Pikachu with all its powerful moves like Twister, Iron Tail, and Facade until Pikachu used the energy from a twister to give Milotic an extremely powerful Volt Tackle.