There isn’t a whole lot you can do to prep for this fight aside from get a few extra moves. If you’re using  Herdier or any other normal type I would highly suggest picking up HM04 Strength from western most house on the south end of the street. Also, the Poke Mart sells extremely useful TMs such as Return, Thunder Wave, Light Screen and Reflect. At this point Return might be more powerful than Strength on your normal type pokes, so I suggest going with that over the HM. Also, be sure to bag a Sun Stone from the house north of the Pokemon Center if you want to evolve Petilil or Cottonee, as the improved stats could turn the tides of battle. And, of course, stock up on Lemonades if you need them. I would highly suggest training to the high 20′s or early 30′s before tackling her.

Now as far as the fight goes, you have to be extremely careful. During these NPC fights, offense is the best defense, but it’s difficult to maintain control of the battlefield as Elesa’s Pokes come with Volt Switch; a strong electric type attack that does damage and switches out with another teammate. Her two Emolga will constantly use it, as well as her Zebstrika along with other attacks. Her female Emolga also comes with Pursuit, which you should be wary of. This attack will do double damage if you’re switching out, which you might find yourself doing from time to time. It’s enough to fill a weakened teammate. Her first Emolga will also use Aerial Ace, which is also a solid attack with 100% accuracy. Her Zebstrika will use Flame Charge from time to time as well, and I believe Shock Wave. Shock Wave is a powerful move to be careful of, because with the STAB it could KO a weak teammate. Elesa’s pokes are also extremely quick, and will more than likely always attack first unless you paralyze them. And if that wasn’t enough, her Emolga come with the Static ability, which will paralyze you upon physical contact. All of these factors make her extremely annoying to contend with, especially if you’re unlucky like me and half of your team ends up paralyzed.

A lot of the more common, useful pokes that you have during this time won’t fare well against her. All three starters will have trouble going against her teammates. Any use of grass, fighting, water or flying types will face problems with her attacks. Drilbur, Roggenrolla, Sandile and Palpitoad are highly suggested to be your main pokes to use for this fight. Even still, they can be killed with neutral attacks fairly quickly..

After dueling Elsa, you’ll get Volt Switch as a reward (you might not have any pokes to take advantage of it, which is sad because by the time you get someone decent enough to use it it’s overshadowed by better attacks). Continue with the story  and make your way to Driftveil City!