There is no way I (AND NEITHER SHOULD YOU!) have to put up with that sort of behavior from someone whom says they love you and want to spend the rest of their life with you.
She sounds like a spoiled brat to me. There is no compassion that whatever if she just goes off about this when she is upset. She needs to learn to keep her emotions in check.
I would not go through with getting married. Since you two have only been dating a few months and are rushing things due to her being pregnant, there is no way in hell that I would get married to her after she's done and said all of that.
Technically, if she's speaking of traditions with who pays for the wedding, the brides family pays for the majority of the wedding anyway. I'm not too keen on that tradition, as I would never ask anyone to pay for my wedding, but that is technically the tradition. The grooms family pays for the rehearsal dinner I think and maybe something else.
There are only a few solutions that I can think of. Postpone the wedding until a later time, after the baby is born. Tell her that you don't feel comfortable having her family pay for it all and that you want to be able to contribute but you need some time to save money. This too will give you some time to see if she is really the person you want to spend the rest of your life with (my vote is no, she's not--so rude what she said).
OR---
You can just simply go through with the wedding. You need to for sure tell her that what she said was not acceptable and make sure she knows that you're not going to tolerate being verbally abused by her speaking this rubbish of your family. She obviously hasn't had to deal with the hard economic times likes most of us have.
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Just make sure you do what is best for YOU. I know it's hard now that you have a baby coming into the picture. You can't let that sway your decisions right now though. That's going to happen no matter what. You have kinda made your bed as far as this woman being in your life forever now by having a child with her (i hate to bring up the point of if the child is yours or not). Although that is true, you don't have to spend the rest of your life with her. You should make that decision before or while the child is young so you don't subject it to your broken relationship with it's mother.
You may really love her and want to try and make it work out. If that's the case then I wish you the best of luck. You can't change people--and this woman is a piece of work.
Good-Luck!
-------------By The Way!!----
You are entitled to RIGHTS as being the child's father even if you don't marry the mother of the child. It will probably get costly, as you'll have to hire a lawyer that will be able to help you decide whats best for you and your legal rights as far as custody would be concerned in the child's life. Although it will cost you some money, it will be well worth it in the end when you aren't married to someone whom you don't want to be married too and your still have rights and partial custody of your child..Again it all goes back to that whole you made your bed and now you have to grow up and live with the consequences, but it will work out in the long run.