D..
Put aside your feelings, Mom. Were you a doormat because you sent her to college in the first place? Honestly, you seem to expect her to be the adult, when you sound like her.
Now, I realize that you are venting here. And that's good, because it's better than venting in front of her. She is in a great deal of pain. Think of it from the prospective of how YOU would have felt if your husband had dumped you oh so long ago. She probably feels that she can't get past her pain where she is now, so she is looking towards another place to help her move past this.
What you told her about money and marriage is spot on. But she is NOT getting married. So tell her that what you would have spent at the original school is what you will pay now. Tell her that if she can't transfer all of her classes and ends up needing to stay longer, the extra is on her. Tell her that 4 years is your max. Look up the figure that you pay per semester and tell her that anything over that is her responsibility if she changes schools. Tell her to make sure she has the money to pay the difference the first semester at the new place before she transfers.
Then say nothing else. Let her do all the legwork. Don't make phone calls for her. She has to want this enough to make it happen.
If you look back on your life, and are honest about it, you "grew up" and then regressed, grew up some more, and then regressed, etc. Indeed, some people regress just being around their parents. It takes time and years for kids to grow up. Personally, I think in some way you should be proud of her for trying to actually think about how she can pay her own way. She obviously did some research into it and found out how hard it would be to do that.
So - show her how an adult acts. Tell her the nuts and bolts. Go back to the original plan. Don't lecture her. Then let her figure it out. What you won't have is a daughter getting married. Isn't that what you wanted in the first place? So don't push her into it by hanging the money thing over her head now.
Dawn