Ricci I'm sorry your having such a hard time trying to help out your niece.

You seem to be really going the extra mile to help her and her unborn baby.
Shes only 22 and may still be a bit immature....being with a man like that proves this.
She really needs to start thinking about herself and her babies safety.
I'm sure this isn't the type of environment she wants for her child, but she's young, has a history with this man, believes she is in love with him, and maybe thinks he'll change. It can be hard to get her to see things differently.
I'm not sure what advice I can give, except that you are doing all you can, and more.
Its obvious you love her, and only want the best for her, but you can only do so much. Don't be hard on yourself for her being moody and unappreciative.
She's probably trying to deal with a lot of emotions right now, and it may be a long time before she clears things up.
The most you can do for her is be there, like you have been.
If she messes up the situation you have helped her to set up, then it's her problem. Not yours. You've done more then your share.
Just let her know, you love her, and your going to be there if she needs you.
Don't get yourself down..she is the one digging the hole deeper.