It sounds like you are attached to something that doesn't exist. She is not who she was, even if that's simply because she stopped drinking, if that was the only factor, that's a huge change.
Let's say her mental illness was depression, that you always knew her as depressed at different levels. Something snapped for some reason and she started to seek help and come out of that depression and wanted to start rebuilding her life.
The person who was depressed for 10 years is not necessarily the same person with the same outlook when the depression is treated or lessened or relieved.
That's kind of how mental illness works. If you are involved with someone who is mentally ill / has a mental chemical imbalance - which I include alcoholism to be, it's kind of a crap shoot. Is that fair, well perhaps not really, but it is a fact.
Originally Posted by
woodlandlost 
I know...be happy for her, give her space and all that stuff.
You don't have to "be" anything. You don't have to be happy for her or anyone else. You don't have to be kind or supportive or anything. If you want to be those things, well that's fine too.
The only thing that you must insist from yourself is that you must not hinder her progress in any way, that's it. The rest is up to you.
You think you are holding on to her tight but that's just in your thoughts you know, you can't hold anyone.
So now back to you. How do you free yourself? First of all, is the way you are approaching this making you at all happy? peaceful? content? Is it adding anything in any good way to your life? Doesn't seem to be, so why are you punishing yourself and you talk about fear, fear of what, that you might have some fun??
I'm not saying you need to rush out and get in to another relationship, but your main focus right now should be you and what you can do to add to your life and your social life and your happiness.
Can you do that?