Halo (Halo Trilogy Series #1)

Three angels are sent down to bring good to the world: Gabriel, the warrior; Ivy, the healer; and Bethany, a teenage girl who is the least experienced of the trio. But she is the most human, and when she is romantically drawn to a mortal boy, the angels fear she will not be strong enough to save anyone—especially herself—from the Dark Forces.
Is love a great enough power against evil?