Good for you, proud mama. And good for your daughter, to be open enough to learn about an idea many conservative Christians would shun as anathema.
One good book that explores the concept of multiple loves from a scriptural Christian viewpoint is Divine Sex: Liberating Sex from Religious Tradition. It's a scholarly work writtten by a person raised in a conservative Christian environment who undertook a systematic examination of the Bible in the hopes of determining what it really says concerning a great many sexual matters. I found it to be very interesting and enlightening.