LOTR is ruining my friendship....

[MLD-Grounds-Keeper-Willie]

one of her trashy Witch Sci-fi novels

Uummm, there's a big part of your problem. Nyneve is right, don't call it that. If you insult her book, it's only fair that she gets to insult yours too. And eleanor_niphredil, Iarwain, Nyneve, The Squatter of Amon Rûdh are right when they say

your friendships are worth more

People are more valuable than stories

You shouldn't have to choose between LOTR and your friend!

falling out with one's friends over a work of literature is demented

So what if she doesn't like LotR? That doesn't matter. You can't let one small difference like that ruin your friendship. It's not worth it, and if you don't realize it now, then you're going to regret it later. Everyone is different, and that's what makes of each of us unique. You should learn to appreciate and tolerate those differences, and possibly even celebrate and embrace them. Don't focus on them, just focus on the similarites you two have. If you let that difference get to you, then it's going to tear you two apart. One questoin I have: have you read her novel, and has has she read LotR?