If she really loves you, she'll get a divorce and move on with you. She's not making any decisions, and you're all stuck in a terrible situation. If she doesn't leave the man she doesn't love and is cheating on, and try and make a new life with you, she will regret it for the rest of her life.
You really need to make her understand that she's also holding back your life too, and the one you could be having with her. If this isn't just some fantasy life where she actually enjoys the emotional rollercoaster of having an affair with her "soulmate" whilst sticking with the husband she "feels sorry for", then she needs to make a decision to move on. Affairs can be exciting and dangerous making a woman feel special, where real life is boring and dull.
You're going to have to force that decision, or you will be stuck in limbo too. Presumably you want more too, not just half a life with her sneaking about behind her husband's back, and you need to tell her that she has to leave her husband and start a new life with you, if she cares anything for you at all. Don't just say you'll wait for her decision, tell her she knows you're the better choice, and that she should pack her stuff and come and live with you. She needs to sort her **** out if she wants to be with you properly.
This is likely to all come out sooner or later and the whole thing will blow up in all your faces, and it's quite possible that everyone will lose out if you don't get ahead of the situation and make it go the way you want it to. If it ends badly she could feel so guilty that it ruins your chance of making a new relationship going forwards.
Thanks for your comments - I've been around the park with this one and gotten bolder with my thoughts on the matter having told her what her choices are. The issue is that i am her best friend and she comes to me for advice as well as our relationship stuff too. She doesn't trust anyone else and won't even discuss it with her parents, female friends or sibling. I try to be pretty impartial, but i'm obviously biased.
She has big mental introvert sessions where she will swing from extremes like: life with her husband isn't 'bad', she just goes through the motions, acts the part and stuff just continues. She doesn't love him, or enjoy him, but merely is familiar and used to him.
She comes out with stuff like "well he seemed happy today, so i'm feeling ok", even though her happiness is what matters not his. As well as the cryptic "I'm not unhappy, but i'm not happy like I am with you."
In her bouts of guilt she bends over backwards to please him or just sits there looking at him comparing him to me, to the 'n'th degree - like our kisses are better, the way we interact physically is better, i'm funnier, i'm more attractive, we have loads of common interests whilst her husband has nothing in common except house/finances etc etc ad nauseum.
The big issue is that he is her first and only romance which they had since they were 13, and she's been with him since (about 14yrs, married 6yrs). People change and can grow apart. I don't actually know her husband, and have never met him, but he seems like a decent chap, if not boring and perhaps looks a little plain.
She comes out with stuff like "well he seemed happy today, so i'm feeling ok", even though her happiness is what matters not his. As well as the cryptic "I'm not unhappy, but i'm not happy like I am with you."
In her bouts of guilt she bends over backwards to please him or just sits there looking at him comparing him to me, to the 'n'th degree - like our kisses are better, the way we interact physically is better, i'm funnier, i'm more attractive, we have loads of common interests whilst her husband has nothing in common except house/finances etc etc ad nauseum.
The big issue is that he is her first and only romance which they had since they were 13, and she's been with him since (about 14yrs, married 6yrs). People change and can grow apart. I don't actually know her husband, and have never met him, but he seems like a decent chap, if not boring and perhaps looks a little plain.