High Wizardry

Young wizards Nita and Kit face their most terrifying challenge yet: Nita's little sister, Dairine. Not only is Dairine far too smart for a ten-year-old, she also has recenlty become a wizard, and worse yet, a wizard with almost limitless power. When Dairine's computerized wizard's manual glibly sends her off on her novice adventure--her Ordeal--Kit and Nita end up chasing her across the galaxy, trying to catch up with Dairine before she gets into trouble so deep that not even her brains can resuce her.
When her younger sister uses the family computer with its special wizard software to travel to worlds light years away, Nita uses her wizardry to try to find her.