Dude if you share a mutual feeling then tell her that you also like her. Simple as that but if you do not share a mutual feeling with her and want to let her off easy then just say: “I really appreciate you telling me honestly but I'm afraid I can't give you the feelings you desire as I only think of you as a friend.” If she wants to be friends still after this whole fiasco then go ahead and be the best goddamned friend you can ever be.But if she wants to be friends no longer then tell her that you will comply with her request but will still miss the joys of her company. Hope it helps u😊👍