Stella Maris by Marita A. Hansen

At her first Confirmation lesson, Catherine Lovich is given a beautiful rosary known as the Stella Maris. Unaware of the danger attached to it, she accepts the gift, soon discovering that each bead on the rosary holds a unique power, powers that only Merges can use. Descended from angels and demons, Merges have the innate ability to manipulate the elements as well as bring the past to the present through dreams.
After meeting Christopher Laboure on her first day back at Agnaru High, Catherine learns that the arrogant but heavenly-looking boy is a Merge—like herself. But unlike Catherine, Christopher is a Seraph, a Merge who controls the fire beads.
When a heated kiss goes wrong, Christopher finds out that Catherine is wearing the Stella Maris—the water rosary his grandfather wants to destroy.
Along with its owner.