Elesa can be beaten multiple ways. You can use one of the fossils from the Relic Castle, use a Dwebble, etc.
If you really want to kick her ass, get a Sandile, train it and evolve it into a Krokorok and use it's Bite/Crunch to beat her Emolga and her Zebstrika can be beaten with a mere Dig.
But if you want to evolve your Boldore, I'll help.