[Lush]

Infedelity, i.e. "cheating" (as in, you come home to discover your wife in bed with the milkman, or whatnot) is indeed problematic, but I can't bring myself to view it in plain terms.
What if, for example, Elrond had met Galadriel on some moonlit stroll through Middle Earth before Galadriel ever married Celeborn, and sired Arwen, or any other Elf-kid? Would you, Rosa, be offended? Of course, we have Celebrian who solves that problem nicely for us, but what if Tolkien had decided to toss her out of the equation? Wouldn't make much of a difference to me, thats for sure. Of course, the story is made richer by her presence, but this is only from a literary point of view. From a "Christian" perspective, I wouldn't give a hoot as to whom Galadriel had loved before she wed Celeborn, as long as she remained, well, Galadriel, fair and wise.
What's truly attractive is the idea that there is a "one true love" for many of Tolkien's characters. Galadriel had Celeborn, Elrond had Celebrian, Sam had Rosie, Arwen had Aragorn, Beren had Luthien, etc. But if one of those characters, Galadriel for instance (as hard as that would be to believe) had a "past" with someone other than her present husband, it wouldn't make the story a lesser one in my eyes.