I'm not sure what the rebound would have to do with anything. Question is, what are your feelings, and have you expressed them to her? Obviously if you are not into the relationship, continuing it is not a good thing.

If you don't see yourself developing any feelings for her then you should end it. She will be upset but she will get over it. Be honest, but kind.

It doesn't sound like you are a jerk. Everyone is subject to acting upon the way that feel at the time that they feel it. How were you to know whether the foundations of love were present here until you had some time to discover who she was? Do not in any circumstances however carry on with it. It is an insult to yourself, and to her and will only make things much worse in the end. You will have to break up with her...something that is always hard to do. Be gentle however. Tell her that you had some feelings at the beginning but didn't quite know what they were. You wanted to get to know her better to see if they developed into love, and for whatever reason they didn't. Thank you for the opportunity to get to know her better, and thank her for observable (and true) positive impacts she has had on your life in the time being...but avoid getting preachy about how "great of a person she is". Too much will cause her to shrug off everything as a pathetic attempt to make her feel better. Maintain both your dignity, and your perception of hers, and offer to be friends if you really want to. Avaoid saying anything that isn't true, and definately avoid any concept of this being a "mistake", a "rebound relationship" or anything of the sort. Consider it a learning experience, and value the time she has given you to determine if she was a match for you. Good luck!