The Saint's Magic Power is Omnipotent (Light Novel) Vol. 1  (English, Paperback, Tachibana Yuka)

Sei, a 20-year-old office worker, is whisked away to a whole new world. Unfortunately for Sei, the ritual that summoned her - meant to produce a 'Saint' who would banish the dark magic - brought two people over instead of one. And everyone prefers the second girl over Sei?! But this is just fine by Sei, who leaves the royal palace to set up shop making potions and cosmetics with her newfound magic. Business is booming, and this might not be such a bad life, after all... as long as her supposed Sainthood doesn't come back to haunt her.