Pokémon Trading Card Game/Grass Club

The Grass Club is an all-girls club of Grass type Pokémon decks. It's a clear analogue to the Celadon City Gym in the mainline games. The club master Nikki isn't here right now, and her club members won't tell you where she is until you defeat all of them.

Kristin
She is on the eastern side of the Grass Club's main hall.

Heather
Heather is right in front of you when you enter the main hall.

Brittany
She is in the Grass Club lounge at the table.

You do not want her to get her Jynx set up to use Meditate. Knock it out as soon as possible if she puts it in play.

The rest of her Pokémon are pretty weak, and have many different types making it difficult for her to get the right energy to use their most powerful attacks. The problem that comes up is that they like to cause the Paralysis status condition, preventing you from attacking on your turn unless you have a card like Full Heal, or Switch with another Pokémon who is ready to fight on the bench or one with free retreat to get your attacking Pokémon back in the active spot.

You want to strike quickly because Brittany will be at an advantage in the late game when she has access to the right types of energy.

Club Master: Nikki
Once you have defeated all three of the other members of the club, they will tell you that Nikki has gone up to Ishihara's house. The house in the northwest of the map will now be called Ishihara's House and you can go there to find Nikki. She says she was doing research and heads back to the club to be able to duel you. She will be at the north end of the room Kristen and Heather are in.

A victory over Nikki results in you obtaining the Grass Medal.

Card Trades
There is a girl in the lounge of the club who wants an Oddish Lv.8 card. She'll trade you a Vileplume Lv.35 card for it. You can get Vileplume in the same Mystery booster pack that you can also find the Oddish in so this isn't a unique trade you absolutely must do, but it is a nice trade of a common for a rare if you're struggling to find a Vileplume.