If you can't be honest with yourself how can you be honest with her and expect a relationship to work? You need to follow your heart and I guarantee it will lead you in the right direction. You simply need to tell her that your friendship will always be there but that you need to move on in order to save that friendship and that if you stay, you both will begin to resent one another and then you won't have the friendship AT ALL and it sounds like that is beginning to happen. Trust me, I know what it's like to be alone and I also understand wanting to stay in an unhealthy relationship just so I don't have to be alone and in the end, because we did this, we ended up never speaking again. Save this friendship before it's too late.