Usually the line I don't want to ruin the friendship is a nice way of saying I am not interested. Anything you "do" to make her love you will be you acting unlike yourself therefore giving a false impression. Stay friends with her do not change yourself, and if she starts to feel something, great, if she doesn't well you have to be prepared for that as well. If it gets to be too much, and you can't even spend a minute with her without being driven crazy by thoughts of loving her perhaps take a break from the friendship as well.