Honestly, I would really hate for someone I care about to just up and poof. I would be horrified, to say the least. I personally feel that at the VERY LEAST one could do is to leave a note explaining why, and just that is a slap in the face because they obviously don't trust me enough, nor love for that matter. ..... Needless to say I am VERY not for the "up and disappear" notion. I'd say give her a chance, at the very least. She might, after all, love YOU, an that would be a horrible thing to throw away. (I have been single for 30 odd years; It hurts to be alone. Honestly, don't throw away happiness without a second thought, such an action might well haunt you later. I think anyway.)
But this all said, yes, it is hard to tell those we love. Honestly, it's best to get used to the hardship as it is all about. But that said, my personal opinion is to say that telling those we love as soon as humanly possible is the best course of action. But then, I despise falsehood, and I for one certainly didn't wake up and throw off the male facade just to slink around the shadows of half truths and out right lies. I am a girl, if people love me, they deal. An you know what? They almost all have. It's certainly not easy, but it's better than the alternative. But then, my frame of mind says that it is better to be hated for what you are, than loved for what you are not.
But that all said, I don't know your life, only the path path I've taken. An I do not regret telling my then fiancée, and subsequently loosing her for the soul reason that she needs a man.
But anyway, I wish you very much luck, and I hope that you will need none of it.