From the way it sounds, you may be a bit insecure and your feelings are causing you to smother her a bit. While this is not the worst thing in the world, it is one of the leading causes of failed relationships. Even though you love her and you enjoy spending time with her, that does not mean that it should be excessive, She is probably not open about the way she feels about it since there is a chance that your feelings may be hurt.
If you truly want to stop your terrible dream from becoming a reality, you must work on your insecurities. Think hard and try assessing the reasons for your fear. Keep in mind that telling someone constantly that they are needed can become emotionally abusive if you are using this to keep them where they do not want to be. While it took her a while to answer your text, that could be for any number of reasons, so do not read too much into that.
Love is an emotion that is felt from within and it is not really necessary to say it all of the time. Once it becomes a part of your routine, it an lose its spark. The two of you should be able to rest easy knowing that the other loves them without the constant reassurance. So to answer your question, no I do not believe that she is falling out of love with you, but I do believe that she feels more secure with you than you feel with her, and that is something you need to work on, especially if she hasn't done anything in the past that would warrant these emotions.