Magic Is Faster Than Light — James Hartley

Megan Bradley and the rest of the witches were rounded up by a religious crusade and forced onto a spaceship for a 190-year multi-generation trip to another star. They soon discovered the ship had problems and would run out of air long before they reached their destination. They were forced to use magic to get to their destination faster, before they suffocated.

But then, of course, they had a whole new world to cope with ...