The Rowan by Anne McCaffrey Book

Book 1 of The Tower and the Hive trilogy. The kinetically gifted, trained in mind/machine gestalt, are the most valued citizens of the Nine Star League. Using mental powers alone, these few Prime Talents transport ships, cargo and people between Earth's Moon, Mars' Demos and Jupiter's Callisto. An orphaned young girl, simply called The Rowan, is discovered to have superior telepathic potential and is trained to become Prime Talent on Callisto. After years of self-sacrificing dedication to her position, The Rowan intercepts an urgent mental call from Jeff Raven, a young Prime Talent on distant Deneb. She convinces the other Primes to merge their powers with hers to help fight off an attack by invading aliens. Her growing relationship with Jeff gives her the courage to break her status-imposed isolation, and choose the more rewarding world of love and family.