Gift of the Unmage (Worldweavers Series #1)

Great things have been expected of Thea, the seventh child of two
seventh children, Now, with Cheveyo, a mage [of the Anasazi], Thea has
begun to weave herself a new magical identity, infused with elements
of the original worlds. But back home, THea keeps her abilities hidden
and attends the Wandless Academy, the one school on Earth for those
who have no apparent magical talent. It is there that Thea realizes
that her enemies are hungrier and more dangerous than she knew. What's
more, her greatest strength may be the powerlessness she has resisted
for so long.