Hi zak,
Sounds like you are between a rock and a hard place here. I think it's commendable that you don't want to leave the relationship just because she has some commitment issues and other things too. But, at the same time, you deserve to be happy and to have some say in your relationships. It can't all be one sided.....it's not healthy that way, as you can see.
How is this situation making YOU feel? Are you feeling used? Are you feeling like a puppet who is expected to drop everything and jump when she says so? Are you feeling like you have no control in your life or relationship? Are you beginning to feel resentment towards her? Are you feeling less self esteem and putting yourself down over this?
We have no control over what others do. We do have control over ourselves. I'm thinking that if you can begin to take back some control over your life and feelings, it should help you be able to come to terms and decisions within this relationship to where you feel more comfortable. It may mean cutting off the relationship....it may mean working harder with her to help the relationship and her actually putting forth some effort as well. Whatever it means for you, until you begin the process of taking back some control, you will feel depressed and lost within this situation.
I hope you find some peace very soon. Take good care!

sabby