First, you will need strong Fighting, Fire and Bug/Dark/Ghost Pokémon or moves, as these 3 types together deal supereffective damage to her entire team.
- Arcanine is probably the best 'mon in itself with Close Combat and Flare Blitz (its only good fire move you can get in S/V without the DLC), dealing 4x to Kingambit, her scariest 'mon, and 2x to half the rest, as well as being respectable in a playthrough, getting it after Fire Star Base.
- Meowscarada or Skeledirge both have STAB moves in Night Slash and Shadow Ball to clean up Espathra and Veluza, and the fact that they are starters means you hopefully have them (otherwise Kingambit is a solid option - none of Geeta's can hit it for x2). Meowscarada is better, as it is immune to Lumina Crash, which can snowball quickly, and resists Veluza's Liquidation and Aqua Jet. However, you will want to Tera, Grass is best, to avoid super effective Dazzling Gleam from Espathra. Then, you can outspeed and hit Veluza with T-Grass Flower Trick, a guaranteed OHKO.
- You may also want to bring some tanky Pokémon, as this strategy hinges pretty heavily on your 2 'mons, so be sure to send a tank out and use a few Max Revives (assuming you can use items, otherwise Revival Blessing is your only option) if one of them faints.
Alternately, just be 10 levels higher than her.
