Lily is one of eight Gym leaders in the Genus Region. Her gym is located in Bellmare city and she specialises in using Grass-type Pokemon.
Although she may be the first gym leader you have to face, she is extraordinarily tough, using a team that's well-suited to taking down beginner trainers.
As well as being a leader, she is also maintaining a strong friendship with Ellen, the water-type Gym leader. This is by no means a coincidence for Lily was inspired to prove herself as a leader because of her friend's lofty position. It's hard for both of them, as they don't get to see each other as frequently as they'd like, being based in different cities, but they're both committed to their duty, at least for the present.