This almost feels like a fake request, but I'll put my two cents in anyway.
Life happens, plans change. I'm sure there was a good reason for the bride to change the locations. I'm betting she didn't do it just to make you and your husband angry or upset.
If you only spent $100 on a dress, consider yourself lucky. That's inexpensive by today's standards. You spent $100 to stand by your friend, no matter WHERE this event is held, right?
Since the standards seemed to have relaxed now, with backyard wedding, Hawaiian shirt, etc. you CAN do your own hair. If she gets mad, she gets mad. But, you're going to be in photographs, so you may want to reconsider this since you were willing to shell out the bucks originally.
"But she is still intent on getting smashed before, during and after the wedding."
She told you this? That's really odd. It just doesn't have the ring of truth, I'm afraid. I'm hoping you're exagerating.
If hanging out with friends in a new dress at a backyard wedding, suffering through not riding in a limo, eating at a "homemade" reception is the worst thing you've put yourself through, honey, consider yourself one lucky woman!
Why does your husband want to back out? He doesn't like parties? He wants to put himself out as a immature guy who can't be counted on?
Stop complaining, show some class, chin up and be the stand up woman you can CHOOSE to be. That's my advice. This is not about you, it's about your alcoholic (by YOUR description) friend. She may need all the friends she can get!